N<>. 6.] DEVELOPMENT OF PARYPHA CROCK A. 307 



At the buccal end there were five or six tentacles, a section of 

 which is shown in the figure. Whether the mouth is devel- 

 oped at this time or later I did not decide. 



Summary and Conclusion. 



In a summary of the results obtained in this study, the 

 following points should be noted : 



1. The medusoicl develops from a bud formed by an out- 

 growth of the body wall and shows itself first in a thickening 

 of the endoderm. 



2. The sex cells in both the male and the female are derived 

 from the plug of ectodermal cells which is formed at the apex 

 of the bud. 



3. The medusoid is never set free and no circular canal 

 is formed, although remnants of four radial canals are quite 

 conspicuous. 



4. The eggs grow by the absorption of the cells of the 

 germinal tissue, a syncytium being thus formed. 



5. The nuclei of the primitive eggs persist as pseudo-cells 

 and are gradually broken down to serve as food for the grow- 

 ing embryos. 



6. The pseudo-cells divide amitotically, but are finally ab- 

 sorbed by the growing egg. 



7. The nucleus of the growing egg is absorbed at an early 

 stage, but is re-formed, after the assumption of the typical egg 

 form, from the fragments scattered through the protoplasm. 



8. Segmentation is very irregular and nuclear division often 

 outruns the segmentation of the egg. 



9. The ectoderm is formed by radial delamination of the 

 two outer layers of cells. 



10. The embryo escapes as an actinula with both basal and 

 buccal tentacles. 



The results obtained in this investigation differ in several 

 points from those of Agassiz, whose description of Parypha cro- 

 cea is the only one that I have found. Clark ('93), to be sure, 

 refers to the eggs and spermatozoa of this species, but gives 

 no account of them. Agassiz states that he was unable to 



