EMBRYOLOGY OF CLEPSINE. 261 



(^Vo)) i'l the supplement to his work, concedes that the polar 

 globules are in some cases formed parthenogenetically, and finds 

 in this mode of production something analogous to the process 

 of rejuvenescence in Diatoms (Auxosporenbildung), which in 

 certain cases is accomplished without the union of two indi- 

 viduals, by a single Diatom. According to this view of the 

 matter, the production of polar globules is a process by which 

 the nucleus is rejuvenated (Verjiingungs process des Kernes) — 

 a phenomenon, not of the maturation of the egg, but of the 

 earliest phase of its development, which may take place either 

 parthenogenetically, or under the influence of fecundation. Its 

 meaning is therefore to be sought in der Enffernung eines T/ieils 

 des Eikerns {-?—) . 



This may be correct, but it is not the only interpretation, nor 

 is it, as I btlieve, the one most in harmony with the phenomena 

 of conjugation, the characteristic feature of which is the addition 

 rather than the removal of substance. This is well illustrated by 

 the first of the above modes of conjugation which, as Biitschli 

 himself claims (xtt)? comes nearest of all to the process of 

 fecundation in Metazoa. In the case of partial conjugation 

 there is no diminution, but simply an interchange — a replace- 

 ment of substance. The object in both cases appears to be the 

 reunion of complementary forces, that have been sundered in the 

 course of multiplication by division. 



The process is then fundamentally the same in both instances, 

 the second case being, so to speak, an abridgment of the first. 



Now, impregnation in both plants and animals consists 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 completed. In what relation 

 then do polar corpuscles stand to impregnation ? That there 

 is no necessary connection between them is in harmony with the 

 absence of such corpuscles in conjugation. I believe that the 

 formation of the " canal cells " (Muscineee, Cryptogamse vascu- 

 lares, Coniferse), furnishes a clue to the above question. 

 Hertwig, Strasburger, Biitschli, Fol, and others, see in these 

 cells a pendant of the polar corpuscles. The formation of 

 these canal-cells is everywhere essentially the same, and may 

 be briefly stated. The entire archegonium arises from a single 

 peripheral cell. This cell, in the ferns, for instance, divides 

 first into an outer and inner cell, the plane of division being 

 parallel to the surface of the prothallium. The inner cell 

 divides again in the same manner as before, thus giving three 

 cells, an outer, inner, and middle cell (central c(41). The 



