380 



FERTILIZATION 





ndooajt 



.inn of 



.rag 



^ H fl\ -or briefly discussed on a later page, under the 

 Y heading, Size and Number as related to Or- 



ganisms. 



As the tissue proceeds along the duct, the 

 cells containing 16 granules undergo a further 

 diminution in the size of their granules, and a 

 change in the number and nature of the gran- 

 ules, so that the cells become more transparent; 

 at the same time the nuclei divide mitotically, 

 Mspmtd (7 chromosomes), giving rise to a tissue of 128 

 cells. The evidence that this increase is by 

 rf mitosis is as follows: 1. At the part of the duct 

 where this change is taking place (Fig. 11) the 

 sizes, form and position (in pairs) of the new 

 * nuclei are what would be expected from mitotic 

 division. 2. The new smaller nuclei, pos- 

 terior to the larger, as yet undivided, nuclei, 

 stain more strongly. 3. Occasionally 7-element 

 spindles can be seen. 4. No trace has been 

 seen of any other sort of division. 



Two or more such tissues as that described fill 

 the duct of the male nema, the number of tis- 

 sues varying with the age of the nema and with 

 the copulatory history. The tissues seem to be 

 of two styles, and, if so, perhaps correspond to 

 the two styles of chromosomes in the second- 

 ary spermatocytes (textus spmtdi, Fig. 2). 



Fertilisation and Syngamy. The two sexes 

 of S. parasitifera seem about equally common. 

 During copulation the male passes the sper- 

 matidian tissues on intact to the female, and 

 afterward they may be seen in the uteri, 



nd OOcyt Fig. 12. Carefully proportioned free-hand sketch of 

 gonads of female S. parasitifera after impregnation. The 

 two uteri, outstretched in opposite directions, are filled 

 with spermatidian tissue. The young ovaries are just be- 

 .Ja Of ginning to function and the ova next the flexures, flex ov, 

 are about to enter the uterus. The spermatidia adjacent to 

 the ova about to enter the uteri have metamorphosed into 

 x g~ spermules, spml, and have taken on the form characteris- 

 tic of nemic sperms as hitherto described. In this case 

 two other cells of the spermatidian tissue nearer the vulva have also begun to meta- 

 morphose, trm, blind end of ovary; flex ov, flexure of ovary; txt spmtd, spermatidian 

 tissue; gl vag, vaginal gland, for which see also Fig. 16. 



.glrag 



Mspatd 



trm or 



spoil 



