24G C. O. WHITMAN'. 



The retrograde metaniorphosis of this vesicle bridges over the 

 gap between the cytode and the cell, and thus enables Hackel 

 to begin liis ontogenetic recapitulation with the lowest form of or- 

 ganic life — the structureless ^lom^r. Beautiful as this theory may 

 seem to be (|jliylogenetically speaking), it certainly has some 

 a-priori as well as a-posteriori objections. The idea (facts for the 

 moment waived) that a cell loses its nucleus and sinks to the 

 cytode-condition, for no conceivable purpose except to establish 

 its phylogenetic lineage with " organisms without organs/' is 

 })lainly in contradiction with the ordinary course of nature. 

 Ontogeny furnishes numerous examples of reversion, but I 

 believe no case in which the reversion is followed by a progres- 

 sion to the same point again. There is of course no objection 

 to the theory that cytodes, sometime in the history of the organic 

 kingdom differentiated into cells, nor can we deny that such a 

 ditl'erentiation is possible at the present time; but such a possi- 

 bility is quite insufficient to sanction the belief that an organism 

 begins its evolution by making a phylogenetic excursion to its 

 ancestral cytode-condition. Besides such an excursion, viewed 

 in the light of facts now w-ell ascertained, loses the last vestige of 

 its supposed significance. 



If the egg, after maturity, sinks to the cytode-condition, then 

 it is certain that it reverts to this primordial state, not only 

 before the first cleavage, but also before each subsequent one. 

 As a result of a perfectly regular cleavage, we should pass 

 through a series of reiterated reversions to the primary condition 

 of life, to the arcuimorula-stage (according to Ilackel), which in 

 its turn, before advancing, would become a conglomeration of 

 undifferentiated cytodes! But recent investigations upon the 

 ])roeess of cell division demonstrate clearly that llilckers " Mone- 

 rula '^ does not belong to the ontogenetic series. It is no 

 ])resumi)tion now to say that those who have supposed that the 

 egg passes through an enuclear condition, have drawn this con- 

 clusion from the negative fact, that a condition occurs in which 

 the existence of the nucleus can no longer be demonstrated by 

 the methods employed ; while those who liave maintained its per- 

 sistence, have confounded the primary cleavage-nueh'us with the 

 germinal vesicle. Hiitschli (..'i'^) has also rejected the Monerula- 

 stage on the ground that, in many cases, the germinal vesicle is 

 not eliminated till after fecundation. 



Van Beneden (J 6) has ])ublished an interesting and able 

 defence of his views in regard to the dissolution of the germinal 

 vesicle, which appeared in the 'Quart. Journ, Mic. Sci. 1S7G.' 

 The results of Van Jieneden's researches on the ovum of the 

 ral)bit and of the starfish (Asterncanthion nibeiis), may be most 

 concisely given in his own words (,',",). " My researches on ihe 



