GAMBTOGENBSIS OP SACCOCIRRUS 6 



The behaviour of the cytoplasmic inckisions has been the 

 object of special attention, and I have also gone into the 

 question of the spermatogenesis, and showed in these stages 

 the presence of peculiar yolk-spheres which are divided out 

 between the daughter-cells at the maturation divisions. It 

 is extraordinary the way such metaplastic bodies are shepherded 

 into two groups during the divisions of the spermatocyte. 



This is the concluding part of this present series of papers. 



2. Previous Work. 



The precocious entry of the spermatozoon into the young 

 oocyte was discovered independently by three observers — 

 F. Hempelmann, and by van Gaver and Stephan jointly. 

 Hempelmann's paper appeared a short time before that of 

 the two other observers. 



Hempelmann has contributed two papers on this subject, 

 one in 1906 (34), and one as recently as 1912 (35). His main 

 conclusions are to be found in the latter paper. He shows that 

 the sperms enter oocytes just after the end of the bouquet 

 stage of the prophases of the heterotypic division. Only one 

 spermatozoon enters one egg. 



Just after the last stage of the prophases of the heterotypic 

 division, Hempelmann describes peculiar granules which 

 originate from the nucleus and pass into the cytoplasm, 

 eventually leading to the formation of yolk. These granules 

 are at first quite solid, grow large, and gradually become 

 vacuolated here and there, so as to form a large number of small 

 granules lying in a single vacuole. It is just after this has taken 

 place that the egg cytoplasm becomes filled with yolk ; speaking 

 of these curious peri-nuclear granules, Hempelmann says, 

 ' so scheint es mir kaum zweifelhaft, dass diese Zellbestandteile 

 mit der Dotterbildung in Beziehung gebracht werden miissen '. 

 With regard to the origin of the peri-nuclear granules Hempel- 

 mann writes, ' Auch der Nucleolus beteiligt sich wohl mehr 

 oder weniger an dieser Dotterbildung, denn gelegentlich zeigt 

 er sich umgeben von kleinen, sich ebenso wie er selbst mit den 



B 2 



