E. MARSH ALLI. — REPRODUCTIVE ELEMENTS. 189 



formation probably rests upon a mistaken interpretation of a 

 process of oogenesis. 



So far as concerns the arclueocyte-cougeries of the Hexacti- 

 nellida, I can confidently state that among the constituent cells 

 in any stage of its growth, there exists not one which, on ac- 

 count of its size or of other external peculiarities, can be recognized 

 as an egg. If it be that so many cells are aggregated for the 

 sake of the nutrition of a developing ovum, this ovum is to be 

 expected to deviate more or less morphologically from the rest 

 as it approaches maturity; however, no sign of such a differen- 

 tiation is noticeable. Further, all the cells in a congeries, large 

 or small, are tolerably uniformly and compactly packed together, 

 so as to directly touch one another ; and where they are some- 

 what loDsely arranged, there is not a trace of any substance 

 between them. So that, I am decidedly against the assumption 

 that some of them are, at any stage of the growth of the con- 

 geries, engulfed among certain others as pabulum. If, after all 

 that, a portion or all of the cells in a congeries giving rise to 

 an embryo are still to be looked at in the light of blastomeres 

 that have arisen by segmentation from a single egg-cell, one is 

 driven to the assumption that the original ovum is, like the 

 blastomeres themselves, as small-bodied as, and indistinguishable 

 from, an archœocyte. Tliis would be very remarkable in an 

 ovum ; and moreover, under that supposition, it become impera- 

 tive to deny egg-nature to the large ovum-like cells described by 

 Schulze and by myself from Euplectella. 



It is idle to go into further speculations. From all that I 

 have seen, I am inclined at present to entertain views similar 

 to those put forward by H. V. Wilson in attempting to explain 

 the nature and origin of the larvse I have discovered in the 



