320 WILSON AND MA THEWS. [Vol. X. 



nearly as favorable as those of Toxopneustes, and affording very 

 convincing evidence. The results of this investigation agree 

 in all essential points with those reached in the case of Toxo- 

 pneustes ; and our conclusions are therefore here presented side 

 by side. 



Our independent but concordant results are opposed to those 

 of Fol on every essential point. After the formatioti of the 

 second polar body the egg-arcJioplasm soon disappears, and no 

 egg-centrosonie or egg-archoplasm {'^ ovocentre'' as opposed to the 

 " spermocentre'^) can be discovered at any subsequent period. 

 There is nothing like a '^ qtiadrille" to be seen, save in donble- 

 fertilized eggs {Toxopjienstes). The archoplasm of the first 

 cleavage-amphiaster is developed entirely from, or under the in- 

 fluence of, the sperm-archoplasm {" spermocejitre'' of Fol), and 

 this is derived, not from the apex of the spermatozoon, but from 

 its base, undoubtedly from the middle-piece {Toxopneustes, Ar- 

 bacid). 



It is, of course, possible that the phenomena of fertilization 

 may differ in different species of echinoderms. The agree- 

 ment between the three forms we have studied is, however, a 

 noteworthy fact, the more striking since the eggs of Arbacia 

 differ considerably from those of Toxopneustes in size, texture, 

 and pigmentation, and since in Asterias the history of the 

 sperm-nucleus and archoplasm differs somewhat from that of 

 Toxopneustes, and in such wise as greatly to strengthen the 

 negative evidence. Comparison of a large series of serial sec- 

 tions of these three forms fixed by various reagents (sublimate, 

 sublimate-acetic, chromic acid, chrom-acetic, Flemming's fluid, 

 Hermann's fluid, picro-sublimate, and Fol's picro-osmic mix- 

 ture) leads to the conviction that Fol's methods were untrust- 

 worthy and his results open to question. Whether so experi- 

 enced an observer can have been misled by double-fertilized 

 eggs, which give a simulacrum of a "quadrille " (see Fig. 4, D), 

 may be left an open question. 



It is proper to add that in the following account the senior 

 author is alone responsible for Parts I and II (Toxopnetistes), 

 and Mr. Mathews for Part III {Arbacia, Asterias). 



