STUDIES OF REPRODUCTIVE ELEMENTS: T. 15 



elenuntx. In tJie case of Cfigs tliis second division occurs genercdly only in 

 one of these cells — the egg-cell — , whdc in the other — the first polar body — 

 this division is suspended, so that there arc noiv fur)ned three cells af 

 uneqnal sizes — a large, single egg-cell and ttni snudl polar bodies, the first 

 of whicli contains eight single chromosomes, while the second polar bod g 

 and the egg-cell each contains oiihj four. 



Thus there is ;i complete parallelism between the e^g and sper- 

 matic cell.'. In both cuses the primary germ cells contain eight single 

 chromosomes, each of which diyides transversely and produces mariv 

 daughter cells — s[)ei-m mc>ther-ce]]s of males and oxnm motlier-cells of 

 females, lliese ctjntnin each eight chroniosrnnes like their inother- 

 cells. They grow to a certain extent aiid thcii two siiccessi\e cell- 

 divisions take place in them, in both sexes, without an intervening 

 restino- stao'e, o-ivino' rise to f(3ur spermatozoa in one case and an ea'a'- 

 cell with two polar bodies in the other. There can therefore be no 

 doubt that the eo-o--cell Math two (ov sometimes bv division of tlie first 

 polar body into two cells, three) polar bodies, corresponds exactly 

 with four s])ermatozoa derived fr<mi a single sperm mother-cell, which 

 again corresponds with the egg-cell Ijefore the ibrmati(Mi of the polar 

 bodies. 



4. Fertilization. 



During the formation of the second ]x)lar body the sperm-cell ])ene- 

 t rates into the body of the egg-cell. 'Jlie ])enctrating point seems t() 

 be quite irregular, but mostly near the place Avhere the secojjd polar 

 body is placed. I ha\^e given three drawings of freshly laid eggs in the 

 body of which a sperm cell is ah'cadv present. In fig. 31 we see 

 at the surface of an (.'<x.i^ tlic sef-ond ])olar spindle, and near it to the 

 right lies a spermatic nucleus. wlii<-1i lias just ])eiicti-;iic(l into the egg ; 



