The spontaneous free-swimming behaviour of the cercaria of Transversotrema patialense was recorded using a high-speed micro-cinematographic technique. The sequential change in configuration of the cercaria was analysed quantitatively and the angular relationships of the cercarial components determined with respect to the trajectory of the organism. The cercaria swims tail-first while the tail stem oscillates through an arc of 100–120° with a frequency of 30 Hz at 24°C. The body region oscillates, almost exactly out of phase, through an arc of 180°C at the same frequency. The two furcae execute alternate effective and recovery strokes so that two symmetrical effective strokes are performed during each propulsive cycle. The Reynolds number of the swimming cercaria was approximately 2. The relative importance of viscous and inertial forces in cercarial propulsion is discussed.

The occurrence of 3 mites (Acari: Astigmata) is reported, from the Central African hedgehog Erinaceus albiventris Wagner, in the Nairobi area of Kenya. Notoedres oudemansi Fain (Sarcoptidae) showed sporadic incidence, affected males particularly and caused high mortality. A description of the male mite is given. Caparinia erinacei Fain (Psoroptidae) was found on 72% of animals on capture but showed very low pathogenicity. Rodentopus sciuri Fain (Hypoderidae) was found in the hair follicles of 46% of 43 animals examined; adverse effects were slight.

The transfer of infective larval stages of helminths via the mammary glands is probably more common than generally recognized. Recent investigations of both natural and experimental infections of various animals have shown that the transmammary transmission of some helminths is a major avenue of infection. Other studies indicate that there are at least 13 helminth parasites which may be transmitted as prenatal infections and at least 17 transmitted via the mammary glands. The majority of these are nematodes. However, in one case the tetrathyridia of the cestode Mesocestoides was observed. In this report the life-cycle and transmission of 2 species of diplostomatid trematodes in the genus Pharyngostomoides is described. The raccoon, Procyon lotor, is the only definitive host; a planorbid snail, Menetus dilatatus, and a branchiobdellid annelid, Cambarincola osceola, a commensal on crayfishes, are intermediate hosts. Records for a period of 11 years are now available for the maternal transmission and longevity of this trematode. During this time one infected female raccoon was maintained in the laboratory on a diet of commercial dog food, sweet potatoes and corn. She produced 25 offspring, most of which were infected with Pharyngostomoides, through the 6th litter. There was a declining number of worms in each litter, ranging from nearly 2000 in one of the 1st litter, to none in the 7th litter. After nearly 12 years she continues to pass a few trematode ova. Rather than assume she has retained the same adult worms for 12 years, it is reasonable to conclude that mesocercariae move through her body and eventually mature in the intestine. Because the mesocercariae have a predilection for the lactating mammary gland, it seems likely that a hormonal influence is present. The transmammary transmission of larvae is a viable alternative in the life-cycles of a number of helminths, and in some instances it is probably the major route of infection.

R. R. Young and A. C. Trajstman wish to point out that in their article which appeared in Parasitology 80, 42531, the figure 50 %, on the fifth line of the Summary, should have read 90%.