192 Prof. L. Hill. The Influence of [Dec. 13, 



After the commencement of fission the follicle may contain numerous 

 egg-like cells, which are probably identical with the giant cells which 

 I have previously described in the ovicell of Crisin. Although it is 

 not impossible that these cells may play some part in the formation 

 of th e secondary embryos, this is rendered improbable, not only by 

 the analogy of Crisia, but still more by the fact that the early stages 

 in the development of the primary embryo take place before such 

 cells can be recognised in the ovicell. 



The following results may be deduced from the preceding state- 

 ments : 



1. The ovicell is not altogether external to the zooecia, as might be 

 inferred from some of the older descriptions of this structure. Its 

 cavity is morphologically identical with the body-cavity of the 

 zocecia, and the ovicell results from the breaking down of numerous 

 septa which at first separate from one another a set of tubes formed 

 at the growing edge of the colony in the same manner as the 

 ordinary zocecia. 



2. The development of the ovicell and that of the embryo normally 

 commence at almost the beginning of the life of the colony. So long 

 as the growth of the first brood of larvae continues there is no develop- 

 ment of new primary embryos ; and the numerous young larva? 

 found in the ovicell are descendants of the single primary embryo 

 which is normally produced in one of the two zooecia first budded off 

 from the primary zooecium. 



3. The process cannot well be interpreted as a form of alternation 

 of generations. A large number, perhaps the great majority, of the 

 secondary embryos are formed by the direct fission of pre-existing 

 embryos, and are not budded off from a compact mass of cells as in 

 Crisia. 



4. Certain remarkable analogies may be detected between the 

 development of the Cyclostomata and that of the Phylactolsemata. 

 Further research will be necessary in order to show whether these 

 resemblances are more than mere analogies. 



IV. " The Influence of the Force of Gravity on the Circulation." 

 By LEONARD HILL, M.B., Assistant Professor of Physiology, 

 University College, London, and Grocers' Research Scholar. 

 Communicated by Professor SCHAFER, F.R.S. Received 

 November 19, 1894. 



(From the Physiological Laboratory of University College, London.) 

 (Abstract.) 



The effect of position of the body upon the circulation of the blood 

 is a matter of daily observation with the physician and surgeon, but 



