138 LOUISE B. WALLACE. 



matid and that even during the growth period the chromosome 

 form should be maintained. Not " only one " but two accessory 

 chromosomes described in this paper have been followed without 

 loss of identity from the spermatogonium through the growth 

 stage, prophase, metaphase, telophase down to the spermatid 

 and they more than meet the above requirements in that they 

 have been traced to their final position in the head of the sper- 

 matozoon. The fact that they become granular and partially 

 disintegrate for a short time in the growth period only shows 

 that the granules, of which they are composed, separate from 

 each other as in the other chromosomes but to a much less 

 degree (Fig. 15). There is every probability that the other 

 chromosomes have genetic continuity just as truly as the acces- 

 sory chromosomes have it but at certain definite periods, possibly 

 of great physiological activity, they take a form which tempo- 

 rarily obscures their individuality. 



Degenerating Cells. 



In my earliest studies upon Agalena I noticed many cases in 

 which the mature spermatozoa seemed to be escaping from their 

 respective cell-bodies and I then supposed that the latter could 

 take no part in the formation of the germ-cells, but that they 

 passed with them into the ducts and served as nutriment. Later, 

 upon examination of some preparations made from another 

 spider, Pholcus plialangioidcs, two kinds of degenerating cells 

 were found in the lumen of the testis, one kind being supplied 

 with brilliantly stained nuclei, while the other kind appeared 

 granular and non-nucleated. These two kinds of cells were 

 looked upon as early and late stages in the process of degenera- 

 tion and the presence of chromatin precluded the possibility of 

 their having originated from the cell-bodies discarded by the 

 spermatozoa. The occurrence of spermatozoa wholly or partly 

 free from their cell bodies was thus explained as a mechanical 

 effect of sectioning with a microtome knife as it seemed likely 

 that compact, resistant bodies like the sperm-cells might thus 

 happen to be dislodged from the soft, protoplasmic mass in which 

 they lie. Whence, then, came the great number of degenerating 

 cells in the lumen of the testis and in the ducts ? An answer to 



