MUSEUM OF COMPARATIVE ZOOLOGY. 463 



brief account. The objection to Biitschli's theory, that the formation of 

 pohir globules is equivalent to the elimination of the " nucleolus," which 

 occurs in many Infusoria as a result of (temporary?) conjugation, is found 

 in the fact that the polar globules are formed independently of fecunda- 

 tion, while the " nucleolus " of Infusoria is ejected as a con&equence of the 

 conjugation. 



The view held by BUtschli, that the production of polar globules is a 

 process by which the nucleus is rejuvenated, — a phenomenon, not of 

 the maturation of the Q^g^ but of the earliest phase of its development, 

 which may take place either parthenogenetically, or under the influence 

 of fecundation, — and therefore that the meaning of this process is to be 

 sought in the elimination of a part of the egg nucleus, is not, according to 

 Whitman, the interpretation " most in harmony with the phenomena of 

 conjugation, the characteristic feature of which is the addition rather 

 than the removal of substance." For this reason the forms both of total 

 and of temporary conjugation observed among Infusoria are fundamen- 

 tally the same, the latter being, so to speak, an abridgment of the former. 



" Impregnation in both plants and animals consists," says Whitman, 

 "in a complete and permanent fusion between corresponding parts of 

 two unicellular individuals, fully analogous to what happens in the first 

 mode of conjugation, with this difference, that polar globules and ' canal 

 cells ' are produced before the fusion begins, or at least before it is com- 

 pleted," but not so in the case of conjugation. " In what relation, then, 

 do polar globules stand to impregnation 1" " That there is no necessary 

 [causal] connection is in harmony with the absence of such corpuscles in 

 conjugation." A temporal relation, however, does exist. Whitman 

 adopts the view which homologizes the " canal cells " of plants with the 

 polar globules. In the former the *' canal cells " stand at the end of a 

 series of asexual generations, the impregnated egg beginning a new series 

 that will end like the preceding. "Just as fecundation in plants is fol- 

 lowed by cell proliferation culminating in sexually differentiated cells, 

 destined to copulate and renew the cycle of changes, — all other products 

 of the proliferation (canal cells with the rest) eventually dying out, — so 

 in Infusoria conjugation is succeeded by reproduction by fission, the ulti- 

 mate products of which are sexually differentiated individuals. The 

 chief diff'erence here is, that in one case (Infusoria) all (1), in the other 

 only a comparatively few, individuals become capable of gamic repro- 

 duction ; but this difference, having reference only to a specialization of 

 function which necessarily accompanies the development of a multicellu- 

 lar organism, authorizes no fundamental distinction. In Metazoa, like- 



