Some time ago, in a short article on maturation in the liver fluke Fasciola hepatica (L.), Sanderson (1953) suggested that development might be gynogenetic on the grounds that she was unable to find any second maturation division nor any polar bodies. Nevertheless, the presence of two large “pronuclei” seemed to point to normal zygogenesis. Unable to come to any definite conclusion the author decided to investigate maturation in another digenetic trematode, Haplometra cylindracea (Zeder 1800) when ample supplies came to hand from class dissections of frogs.

Assemblages of small spores are described from the Pumpherston Shell Bed, the Pumpherston Oil Shales, the Burdiehouse Limestone and a thin coal found within the latter rock in one locality, all from the Lower Oil-shale Group (Viséan) of the Lower Carboniferous of Scotland.

The assemblages from the Oil-shales and the Limestone, rocks generally regarded as being of non-marine origin, are found to be very much alike; and although they show some differences from that of the Pumpherston Shell Bed (a marine shale), all three assemblages have a general similarity of composition. A suggested relation is put forward between this uniformity and the conditions prevailing in the area of the Midland Valley of Scotland during deposition of the beds. Correlation with other areas is discussed. Five new species and ten new types are described.

The humoral mechanism controlling metamorphosis in larvæ of Calliphora vomitoria L. and Lucilia cæsar L. and controlling diapause in the latter has been investigated by experiments involving extirpation and implantation of certain organs and section of nerves to the corpus cardiacum. It is confirmed that the large lateral cells of Weismann's ring, the thoracic gland cells, produce a hormone which promotes the several processes covered by the term “pupation”, including the development of anlagen before puparium formation, puparium formation, the third larval moult and the last larval moult. The stimulus to thoracic gland activity is provided by the brain and is transmitted via the nerves from that organ to the corpus cardiacum. This stimulus is apparently humoral and is liberated from the corpus cardiacum into the blood.

The thoracic glands of L. cæsar larvæ are inactive during diapause. Implants of active C. vomitoria glands into L. cæsar diapause larvæ terminate diapause in the latter. The immediate cause of the arrest in development is the failure of the brain to activate the thoracic glands.

Analyses of winter and summer vertical migrations of Meganyctiphanes norvegica are given and the differences in behaviour pointed out. A vertical layering of size classes, larger specimens occurring deeper than smaller ones, is shown to exist during the day and night.

Four potential methods of feeding were found. The inter-relationships between vertical migration, feeding method used, and type of food eaten are discussed.

The relationship of carapace length to total length was found to depend on the state of maturity of M. norvegica.

M. norvegica matures at the age of 1 year, transference of the spermatophores taking place in January-February, the eggs being laid in March-April. The larvae take 2–3 months to reach adolescence and little growth in size takes place in the winter when the gonads are maturing. An age of 3 years may be attained but most only survive 1½—2 years.

The distribution within the Clyde Sea throughout the year is described. Most of the population were found to move to the North-east Arran Area for egg-laying.

A 24-hr. and annual periodicity of luminescence is described and correlated with the period of swarming of this species prior to spermatophore transference.