202 SUMMARY OF CURRENT RESEARCHES RELATING TO 



pecking motion of the anterior end, the cercariffi from the Annelid, 

 occasionally, after lying motionless for a time perform exceedingly rapid 

 wriggling movements." The anterior end bears a short rectractile 

 boring apparatus. What were interpreted to be striated muscle fibres 

 were observed in the tails of the cercarit\3. 



Incertse Sedis. 



Variations in Sperifer mucronatus.* — C. C. Mook has studied 

 five mutations of this fossil species, seeking by statistical methods to 

 determine their relations to one another and the progress of evolution 

 along the different lines. A diagram sums up the relationships. The 

 tendency has l)een to reduce the shell index, to reduce the number of 

 plications, to lose the groove and plication on fold and sinus, and to a 

 certain extent to reduce the actual width of the shell. 



Early Stages of Cephalodiscus.f — J. I). F. Gilchrist contributes 

 some very interesting observations on the Cape species, Cephalodiscus 



gilckristi,'^ with special reference to the larva;. The normal habitat 

 appears to be rocky ground in rather shallow water, below low- water 

 mark. It is either attached to rock or to some substance growing on 

 rock, but may become detached and carried on to muddy ground. It 

 seems to be abundant on the south coast. It may grow from a small 

 basis, or the basis may be a broad sheet of coencecial substance from 

 which several main stems arise. 



In the living state the zooids and buds have been observed on the 

 general surface of the ctcncecium outside the tube, and sometimes at a 

 distance from it. The buds in such cases act as anchors, being firmly 

 adherent to the surface by their proljoscides. In both bud and zooid 

 a quantity of viscid mucus occurs between the proboscis and the 

 ccencecium. 



There is no evidence that the buds ever develop into normal zooids, 

 and they may be individuals specialized for adhesive purposes and 

 coenoecium-building. More than one zooid and its buds may occur in 

 one tube in the coenoecium in the Cape species. Buds and zooids are 



• provided with cilia over the whole of their surface. Their stolons or 

 stalks are also ciliated. The method of feeding is that particles are 

 carried by means of these cilia to the arms, where a selection is made of 

 the food-particles, which are returned to the mouth by the grooves in 

 the arms. The zooids and luids are black in the living condition, but 

 the colour dissolves out very quickly in preservation. 



The eggs are enclosed in a capsule, which is adherent by one end to 

 the wall of the tube. The embryo is ciliated and coloured at an early 

 stage, the older embryos being folded on themselves. They rotate 

 actively in the egg-capsule. The free larva is elongate, ovoid, and 

 usually narrower posteriorly, where an indentation is usually seen. An 

 apical sense-organ appears early in the embryo, and is present in the 

 larva in the form of a white area surrounded by a dark ring of pigment- 



* Aun. New York Acad. Sci., xxvi. (1915) pp. 175-214 (8 figa.). 

 t Ann. Mag. Nat. Hist., xvi. (1915) pp. 233-46 (1 pL). 



