26.2 C. O. WHIIMAN. 



outer cell divides into four, each of which gives rise 

 to a column of cc'ils which together form the neck of the 

 Archegonium. The inner splits into a number of cells which 

 form the body-wall of the archegonium, within which lies the 

 central cell. The latter divides twice, producing the two canal- 

 cells and the egg. 



Of all these cells having a common pedigree, only one — the 

 egg — is destined to survive. The canal-cells are the first to 

 sufi'er disintegration, after which impregnation takes place. Is 

 there anything in all this to justify the assumption that the 

 canal-cells are produced for the purpose of removing a part of 

 the egg-nucleus ? Why assign such a function to these cells, 

 to the exclusion of all the others, since they all have the same 

 origin, and are produced in precisely the same manner? The 

 case is plain ; the canal-cells stand at the end of a series of 

 asexual generations; the impregnated egg begins a new series 

 which will end like the preceding. It is easy here to find a 

 parallel with the events initiated by conjugation. 



Just as in plants, fecundation is followed by cell- proliferation 

 culminating in sexually differentiated cells, destined to copulate 

 and renew the cycle of changes, all other products of the pro- 

 liferation (canal-cells with the rest) eventually dying out; so in 

 Infusoria conjugation is succeeded by reproduction by hssion, 

 the ultimate products of which are sexually differentiated indi- 

 viduals. The chief difference here is, that in one case all (?), in 

 the other only a comparatively few, individuals become capable 

 of gamic reproduction ; but this difference, having reference only 

 to a specialisation of function which necessarily accompanies the 

 development of a multicellular organism, authorizes no funda- 

 mental distinction. In the Metazoa, likewise, a gamic cell- 

 generation is followed by a line of agamic generations, the last 

 of which are the small cells called by Robin polar globules. 

 With the production of these globules we arrive at the sexually 

 ripe egg. In accordance with all this I interpret the formation 

 of j)olar globules as a relic of the primitive mode (^ asexual 

 reproduction., which normally precedes fecundation, and is there- 

 fore no part of the process of nnprcgnation. This interpretation 

 accounts for the otherwise inexplicable fact that amphiastral 

 divisions of the nucleus introduce the formation of the directive 

 cells, and is in harmony with the absence of such cells among 

 Infusoria, and their general occurrence among plants and 

 animals. 



The two poles of a nuclear spindle are the exact counter- 

 parts of each other, and the division of the archiamphaster 

 cannot, any more than the division of the primary cleavage- 

 nucleus, be regarded as a removal of nuclear substance. The 



