76 THOS. H. MONTGOMERY jr., 



whether each represeuts morphologically one segment or two segments 

 of the spirem thread, remains to be ascertained ; on this point depends 

 the question as to whether the chromosomes appear in the normal 

 number or half this number in the spermatocytes. 



In Pentatoma I have shown that half the normal number of 

 chromosomes appears in the 1st spermatocytes, and that in the re- 

 duction divisions each chromosome becomes transversely divided. 



Finally, a word as to the doubtful cases spoken of above. In 

 ÄUolohophora (Foot, '94) only a few lines are given on the mode of 

 reduction of the chromatin, which do not serve to explain the process 

 in any way. In Styeiopsis (Julin, '93) such diJ0ferent modes of re- 

 duction have been described for the ovogenesis and spermatogenesis, 

 that further corroboration of the description must be awaited. Ishi- 

 kawa's observations ('91) on Diaptomus are so different from those of 

 Hacker, Vom Rath and RIjokert on Copepoda, that it would seem 

 that they contained some error of observation. I have not seen 

 Toyama's ('94 b) full paper, and so cannot pass any judgment upon 

 his observations. Platner's ('86) observations, if they be correct, 

 present a very remarkable case of chromosomal division : the 30 chromo- 

 somes of Sphinx and Pygaera, in the prophase of the 1st spermato- 

 cytic division, are dumbbell-shaped, and become arranged in the 

 monaster with their long axes parallel to the spindle; but the meta- 

 kinesis does not divide the chromosomes transversely, but longitu- 

 dinally, i. e. there is a lateral division of the chromosomes — a mode 

 of division which has not again been found in any case. I am in- 

 clined to think on this account that there must have been some error 

 of observation in this case; thus his fig. 15, supposed to be the meta- 

 kinesis of the 1st division by Platner, might be the monaster of the 

 2nd division, in which case a longitudinal division of the chromosomes 

 had not been seen at all; and the early appearance of the transverse 

 constrictions on the chromosomes, would lead to the conclusion that 

 at least one transverse constriction must occur in these cells. 



The recent observations of Giardina ('97) on Mantis are some- 

 what difficult to understand, and as no figures are given, it will be 

 necessary to await his fuller communication. 



The examination of the preceding cases suffices to show, that if 

 the term chromosome be used in the sense in which it is generally 

 applied in more primitive mitoses, — and it must logically be used 

 in this sense, there is possibiUty for greater agreement in the esti- 

 mation of the value of the reduction processes, The following con- 



