1903.] On the Cytology of Apoyamy and Apospory. 



457 



irregular growth of the new tissue, and with the sporadic appearance 

 of sporophytie members, on the prothallium already described by 

 Lang. 



When the nuclei of the cells in the apogamous regions are examined 

 in course of karyokinesis, they are seen to possess a much larger 

 number of chromosomes than those of the ordinary tissue cells of the 

 prothallium. Owing, however, to the manner in which the very 

 numerous chromosomes are distributed on the spindle, an exact estima- 

 tion of actual numbers is a task of considerable difficulty. There 

 appear, however, to be forty and eighty in the respective classes of 

 nuclei. 



We regard the whole process as a kind of irregular fertilisation. The 

 doubling of the chromosomes receives an explanation strictly analogous 

 to that afforded by the normal fusion of oosphere and spermatozoid. 

 But instead of one cell only (the oospore) serving as the starting- 

 point for the new generation, a number of such units loosely co-operate 

 to produce it. And in this connection it is perhaps significant that 

 the young plantlet is commonly borne on, and produced from, a 

 special sporophytie outgrowth, of which the constituent cells may have 

 become homologously differentiated into a sort of pro-embryo. 



Instances are not wanting amongst lower animals to show that 

 close cellular in-breeding may occur, and form part of the normal 

 sexual series of events. It is not desired to press the analogy of such 

 cases ; but the case of Aetinosphaerium shows that a process indis- 

 tinguishable from normal sexual fusion may occur between sister cells 

 that have only lately arisen from the division of a parent cell. 



We do not propose to enter on a full theoretical discussion of the 

 bearings of these observations at the present time, but we hope to do 

 so Avhen we are in a position to deal completely with the corresponding 

 cytological features associated with apospory. 



