2G0 C. O. WHITMAN. 



concludes that it is untenable in view of the so-called bud con- 

 jugation (" kH()S[)eMfr)rinige Conjugation ") of Vorticella. Here, 

 where a complete and permanent fusion of two individuals 

 occurs, we should expect (according to Hertwig's theory) to 

 find only a nucleolus in one (the male) and only a nucleus 

 in the other (the female). This however is not the case, 

 each individual possessing both nucleus and nucleolus. While 

 this fact seems to render the view of Hertwig untenable, 

 it is quite reconcilable with the theory of Engelmann, that 

 nucleolus plus nucleus are equivalent to the ordinary nucleus, 

 the only difference being that in one case both elements remain 

 united, while they differentiate and separate in the other. 



It is first of all important to know which of the above modes 

 of conjugation is to form the basis of comparison. Shall it be 

 that of complete and permanent fusion, such as has been 

 observed in Stylonychia (^V)j ^^^ ^"^ Vorticella nebulifera 

 (tW)* where corresponding parts coalesce? or shall it be that 

 of incomplete and temporary union, which consists in an 

 exchange rather than a fusion of elements ? With reference 

 to the latter and more common mode of conjugation, Biitschli 

 has ventured to compare the ejection of the nucleolus ("secondary 

 nucleus," Infusoria) with the production of polar globules by the 

 egg-cell (jtV). " Wir sahen bei einer Anzahl Infusorien in Folge 

 der Conjugation, eine vollige Ausstossung des secundiiren Nucleus 

 stattfinden und haben anderseits beobachtet, dass nach der 

 Befruchtung der Kern der Eizille eliininirt wird. Wir vnirden 

 nicht anstehen, diese heiden Erscheinungen in ndheren Znsam- 

 menhang zti bringen, wenn eben bis jetzt eine grossere Ueber- 

 einstimmung dariiber erreicht ware, ob die Kernausstossung der 

 Eizelle thatsiichlich eine Folge der Befruchtung sei." 



The objection to this theory, here anticipated by Biitchli, 

 has recently been placed in a stronger light. The fact that the 

 ejection of nucleolus-seginents is a consequence of conjugation, 

 while the production of polar corpuscles is, at least in a few well 

 ascertained cases, entirely independent of fecundation (this is 

 always the case with the "Canal-cell," the supposed homologue 

 of the polar globule), seems to be quite irreconcilable with the 

 above theory. 



Minot (119), who aj)])ears to have accejjted the view suggested 

 bv Biitschli, sees a contirniation of the same in the formation of 

 the Kernspindle ! Hoto the formation of a nuclear spindle 

 confirms tlie supposed homology betvveen polar globule and the 

 nucleoli of Infusoria is not explained. It simply proves the 

 fact that we have to do with nuclear substance in both cases, 

 but confirms the homology in question no more than it confirms 

 a homology between ectoderm-cells and entoderm-cells. lUitschli 



