208 CHITONID.E. 



subglobular figure, and taken that of a subelongated 

 oval, approaching the shape of an adult Chiton. When 

 the swimming-action commenced, only half the animal 

 was liberated from the capsule or membranous integu- 

 ment, the other half being still enclosed, with the empty- 

 portion of the capsule folded over it. With a power of 

 300 linear Mr. Clark saw the elements of the four an- 

 terior valves, as well as the buccal depression and head ; 

 at this stage of development he could not perceive any 

 metamorphosis. In the course of the next five days 

 the animal had altogether cast ofi" the embryonic cover- 

 ing, when it exhibited the complete form of a Chitorij 

 and adhered to the bottom of the vessel. He apparently 

 did not at any period detect the eyes which Loven had 

 noticed. Mr. Clark further remarked that the fry 

 during its phase of rapid movement often rolled itself 

 into a ball. The slight discrepancy betw^een these ob- 

 servations of the Sw^edish and English naturalists may 

 be accounted for by those of the former being more 

 complete, and perhaps having been made under more 

 favourable circumstances. Twenty years ago Milne- 

 Edwards published, in conjunction with Quatrefages 

 and Blanchard, the result of anatomical and zoological 

 researches made on the shores of Sicily and France. 

 Chiton was one of the subjects of their investigation ; 

 but I am not aware that any details were given. Milne- 

 Edw^ards was induced, however, by these researches to 

 declare that he had arrived at a different conclusion 

 from that which was hazarded in the ^ Vestiges of Crea- 

 tion,' viz. that the embryo of the higher animals, in- 

 cluding man himself, presented in succession modes of 

 organization analogous to the permanent state of the 

 principal lower types of the animal kingdom. On the 

 contrary, he w^as of opinion that the embryos of the Mol- 



