1884.] 61 [Hyatt. 



by Schultze in Halisarca previously. He mentions and figures 

 this body in Leucoselenia poterium pi. 3, f. 2, among the Ascones, 

 in Leucilla uter, pi. 6, f. 2f, and writes that he has seen and stud- 

 ied it in most species of Sy cones. Polaejeff in his first paper 

 considers that the primitive nucleus in the cell which gives rise 

 to the spermatocyst divides into two parts, one of which 

 becomes by division the spermatocyst or " Ursamenzelle," and the 

 other is transformed into a "Deckzelle." This Deckzelle or 

 cover-cell has many nuclei and spreads around the cyst and forms 

 the envelope, which he considers to spring from it. Schultze 

 compares the covering membrane in Halisarca lobularis with that 

 of the egg, and we have still farther carried out this comparison 

 by finding in Chalinula a distinct opening similar to the micro- 

 pyle which probably marked the site of some former attach- 

 ment to the mesoderm. Polaejeff makes an apparently strong 

 objection to the gonoblastic theory founded on the cover-cell. 

 We think this may possibly be explained as an optical error, 

 due to the way in which the specimen was viewed and that no 

 such cell really exists. We suggest this without disrespect for 

 the unquestionably superior character of Polaej erf's work, first 

 because we have a drawing of the ovum of Suberites in which 

 the micropyle seen from the side has exactly the aspect of the 

 cover-cell in the figure of the spermatocyst of Leucilla uter (Rep. 

 Chall. pi. 6, f. 2f), but no granules are shown ; and second, because 

 in our observation on the spermatocyst we looked from above 

 directly down and into the interior of the spermatocyst without 

 seeing any nuclei or granules. If there is not a covering-cell, it 

 is probable that the spermatozoa are really developed out of the 

 peripheral nucleus itself, and that the internal nucleus does not 

 help in forming their bodies, whatever their office may be in 

 other respects. 



Polaejeff 's farther objections to the gonoblastic theory rest 

 upon several cases in which the spermatozoa appear to arise from 

 the protoplasm of the cyst and not from the nucleus. Bergh, 

 (Vidensk. Medd. Naturk. Foren. Copenhagen, Aarene 1877-78, p. 

 192, pi. 3), describes and figures the spermatozoa as arising out of 

 the protoplasm of the cyst separated from the nucleus. Klein- 

 enberg, however, saw the first stages in the development of the 

 spermatocyst of Hydra and figures these in his work on Hydra. 



