Ookinesis in Coreliratnlns Lactens. 371 



mitosis described by van der Stricbt ('98), Byrnes ('99) and others, 

 Avhile type B conforms in every respect to the mode of aster-divi- 

 sion in large blastomeres of onr form, which I shall deal with 

 later on. 



(6) Literature and General Remarhs. 



Despite the fact that numerous studies on spermatogenesis have 

 been carried out, and that the fate of the spermatid-centriole in the 

 formation of the spermatozoon has been followed with great accuracy, 

 yet surprisingly few cases are known, in which the centriole of the 

 spermatozoon has been uninterruptedly traced to the sperm-centriole 

 in the egg during the fertilization processes. 



Thanks to the older investigators such as Flemming, Fol, O. Hert- 

 wig, it has long been known that the sperm-rays centre towards the 

 middle-piece. At one time it was thought that the middle-piece as 

 a whole was the sperm-centrosome (Doflein, '97, p. 206; R. Hertwig, 

 '98; Boveri, '00). The relation between the middle piece and the 

 centre of the sperm aster was*made clearer in the works of Henking, 

 ('90), Fick ('93), Wilson and Mathews ('95), Wilson ('97, '99), van 

 der Stricht ('02, '04). There are, however, but five forms in which 

 the centriole has satisfactorily been traced. Hill ('95) observed the 

 centriole in the middle-piece in PJiaUiisia mammilata and traced it to 

 the centre of the sperm aster (PI. 17, Figs. 13a, 21a-f). His 

 description and figures are, however, insufficient to give a clear idea 

 of his observations. Kostanecki and Wierzejski ('96) saw a cen- 

 triole in the middle-piece of the spermatozoon in the gonad of Pliysa 

 fontanaJis, and in a few cases they found the same granule in the egg 

 with rays around it (pp. 338-339). Erlanger ('97) demonstrated 

 the centriole in the spermatozoorT of Ascaris megalocephala and 

 traced it to the fertilization stages (pp. 316-320). Boveri ('00) 

 states that one or two granules are found in the middle-piece of the 

 spermatozoon of Strogylocentrotiis liriduft (his PI. 1, Figs. 14d, e, f, 

 h; PI. A., Figs. 55 a, b; PI. 5, Figs. 71, 72). The same granule 

 (centriole) he ol)serves in the conti"o of the s]ierm aster (his PI. 4, 

 Figs. 55b, PI. 5, Figs. 71, 72). Foot and Strobell ('02, '03) found 



