DESCRIPTION OF BFHVDATIA BLEMBINGTA. 89 



Or doe.s it arise from more than one class of mesoderm 

 cells y 



Or^ finally^ is it bnilt from different germ layers (two or 

 three) ? The gemmule should then be considered a bud. 



In Section III of the second part of this paper I shall give 

 an account of the development of the gemmule in Ephy- 

 datia blembingia, reserving criticism of whatever kind to 

 Section IV. In Section III I shall include nothing but a 

 simple description, followed by a few conclusions. This 

 course will be pursued in order to make the account more 

 available and more intelligible to the reader than it would be 

 if it were mixed up with critical remarks and conclusions 

 scattered about throughout the paper. 



III. Descriptive Account of the Development op the 

 Gemmule op Ephydatia blembingia. 



(1) Origin and Further Development of the Eepro- 

 ductive Part of the Gemmule. — The first sign of prepara- 

 tion for the formation of the gemmule consists in the presence 

 of single cells or small groups of cells scattered about chiefly 

 in the dermal membrane ; the strands of tissues which support 

 the dermal membrane ; and in the tissues situated immediately 

 below the subdermal cavity. 



The protoplasm of the cells in question is uniformly clear, 

 and the nucleus is granular and not vesicular (PI. 2, 

 fig. 8) . I have been unable to detect a karyokinetic figure in 

 any of these cells. Consequently I am of opinion that the 

 constituent cells of these groups seldom divide during the 

 early stages of formation of the gemmule, which is contrary 

 to what must have been the case if the cells of the repro- 

 ductive part of the gemmule were derived from one mother- 

 cell. 



The cells in virtue of their power of wandering travel 

 through the dermal membrane, and strands of tissue which 

 support the membrane, and become aggregated in groups 

 situated either deep in the tissues of the sponge or even in 

 the strands of tissue above mentioned (PI. 2, tig. 8). 



