Boring sponges excavate calcium carbonate substrates by chemical and mechanical methods. The chemical phase of excavation is accomplished at the cellular level by a localized secretion (possibly an acid or an enzyme) at the cell-substrate interface (Cotte, 1902; Nassonow, 1883, 1924; Warburton, 1958; Rützler & Rieger, 1973; Cobb, 1969, 1971, 1975). Chemical etching detaches a chip of calcium carbonate (about 40–60 µm diameter) which is then mechanically removed from the substrate through the sponge tissue and out through the excurrent canal system. Only 2–3% of the substrate is dissolved by the etching cells (Rützler & Rieger, 1973), while the rest is removed as characteristically shaped chips. Recent studies of the mechanism of sponge boring have denned (using light microscopy) the spatial relationships sponge cells establish with the substrate (Cobb, 1971), identified (using transmission electron microscopy) the cell type (etching cell) responsible for chemical etching (Rützler & Rieger, 1973), and described (using scanning electron microscopy) the architectural nature of substrate destruction by sponges (Cobb, 1969, 1971, 1975; Rützler & Rieger, 1973; Pomponi, 1976, 1977, Ph.D. Thesis, University of Miami).

Etching cells of boring sponges effect the excavation of calcium carbonate substrates by partial chemical dissolution. They are characterized by the same features found in active osteoclasts, the cells which effect bone resorption in vertebrates. These similarities include a region of numerous cell processes and a system of cytoplasmic bodies, vesicles, and vacuoles which are structurally connected with a tubular system and with extra-cellular channels (Pomponi, 1979). An extensive rough endoplasmic reticulum, Golgi complex, and lysosomes indicate that a lysosomal system is operative (Pomponi, 1979). The lysosomal system has been implicated as the primary mechanism in the destruction of calcined tissue by osteoclasts (Vaes, 1968; Hancox, 1972, Gothlin & Ericsson, 1976; Holtrop & King, 1977). Vaes (1968) proposed that acid hydrolases of lysosomes are active in the resorption of the organic matrix of bone.

Few studies have been reported on the predatory habits of planktonic foraminifera or on their position in marine food webs. Planktonic foraminifera are large marine Sarcodina possessing a calcium carbonate shell (usually < 1 mm diam.) surrounded by a dense halo of rhizopodia that in some species may increase the cell diameter to 20 mm. Food organisms are snared by the sticky rhizopodia which entangle the prey and draw it into a dense layer of cytoplasm near the shell where digestion occurs (Anderson & Bé, 1976). Clearly species survival, their abundance, and their distribution in a region are deter-mined by the availability of food organisms, so that species that prey on a wide variety of organisms have greater survival advantage than those with a more restricted range of prey. Hence, many of the traditionally studied topics in foraminiferal research such as species abundance, survival time, geographical distribution and contribution to calcium carbonate sediments may be significantly determined by foraminiferal trophic activity. A clearer understanding of foraminiferal predation may help to explain ancient and modern assemblages of species and thus contribute to a more systematic interpretation of foraminiferal ecology.

In a previous paper (Boney, 1961) an account was given of some experiments and observations carried out on the lichen Lichina pygmaea Ag. growing above M.T.L. on the east-facing side of the Church Reef (= Blackstone Rocks) at Wembury, South Devon. The experiments were initiated in the summer and autumn of 1952 and 1953. Experimental sites were prepared by removing rectangular areas of lichen growth from within larger mats, and by clearing away half the lichen growth from small circular patches of about 10 cm diameter. Subsequent observations were re-ported after intervals of 4–7 years (to July 1960). The more obvious results of the clearances made within lichen mats were the failures of the surrounding plant growths to recolonize the cleared areas after 4 years and the disappearance of lichen cover from the borders of one of the cleared areas. The presence of Fucus spiralis L. plants growing in mats near cleared areas indicated that the damage inflicted on the lichen growths had set in train an irreversible series of events. With small circular patches of about 10 cm diameter cleared of half their lichen cover no changes were observable after seven years in both the cleared areas and in the remaining lichen growth. Since 1963 my visits to the experimental sites have been somewhat sporadic. The present note describes observations made up to July 1976, 24 years after initiation of the first clearance experiments.

During our studies of the reproductive cycles in limpets (family Acmaeidae) we have been confronted by the lack of a method to determine sex without killing the animals. Previous studies have relied upon dissection or histological sectioning to determine sex. This note describes a technique which allows the determination of sex in patellacean limpets without killing the animal.

The tools needed are a syringe (1 cc) with a hypodermic needle (we have found that a 26 gauge, 16 mm needle works well with specimens larger than 10 mm in length), and a glass microscope slide. After removing the limpet from the substratum the shell is held with the aperture down. As the animal extends its foot downward it exposes and stretches the sides of the body wall. When the posterior portion of the body wall is fully exposed the needle is inserted approximately one third of the way up the body wall towards the shell attachment muscle. The orientation of the needle should be in line with the plane of the aperture. Penetration of the gonad can be felt by a ‘breaking through’ or sudden decrease in resistance to the progress of the needle. Care should be taken to avoid penetrating further than necessary because other organs can be easily damaged. Drawing the sample requires more force and time (approximately 10 s) than one would expect. When withdrawing the needle constant tension on the syringe plunger is necessary to keep the sample in the needle. The contents of the needle are then emptied on to the glass slide.