1905.] NATURAL SCIENCES OF PHILADELPHIA. 181 



tional mitosis, a separation of whole univalent chromosomes, occurs in 

 many objects. In all the works where two successive equational divi- 

 sions have been described, it is significant that no positive explanation 

 has been given of the earliest mode of origin of the bivalent chromo- 

 somes, not even in the detailed study of Brauer (1893), and the same 

 may be said of the recent elaborate analysis of de Sinety (1901). All 

 the "cumitotic" investigators seem to have interpreted as a first longi- 

 tudinal splitting of the chromosomes a space which they have not 

 proved to be such, and which the observations of others show to be in 

 all probability the space between two conjugated univalent chromo- 

 somes. They likewise fail to account for the fact that the chromo- 

 somes in the reduction divisions so frequently differ in form from all 

 other chromosomes, and leave undecided the question of the origin 

 of the bivalent chromosomes. It is not necessary to go further into 

 detail here upon this point, on which I have expressed myself many 

 times previously. But we can say positively that there has not yet 

 been proved any case of eumitotic maturation in the sense of Korschelt : 

 that even in Ascaris, the foundation-stone of this doctrine, Sabasch- 

 nikoff (1897) has shown that Boveri (1888), Hertwig (1890) and Brauer 

 (1893) may have given a wrong analysis, while recently Boveri (1904) 

 himself and I (1904a) have argued for the probable occurrence of a 

 reduction division here; and for the vertebrates also Iving (1901), 

 Schreiner (1904), Marechal (1904) and I (1903, 1904a) have proved the 

 same contention. While this dispute will not be settled for some time, 

 for the reason that scarcely a beginning has yet been made in the study 

 of the germ cells, I do not hesitate to declare that in none of the Metazoa 

 does maturation of the eumitotic type occur. And I make this pro- 

 phecy after starting from the point of view (1898) that there may 

 well be different modes of maturation, and consequently I can surely 

 not be accused of starting out on my studies w^ith bias in any particular 

 direction. 



Further, all evidence of any strength is to the effect that probably in 

 no case are both maturation divisions reductional. This standpoint 

 has been held by Wilcox (1895) and a few others, and by myself in my 

 first paper (1898), but I quickly discovered and corrected this initial 

 error (1899). To this "Correction" another correction must be made: 

 in the note of 1899 I wrote that the second maturation may be occa- 

 sionally reductional, occasionally equational; this was a mistake, for 

 now I can say there is in Pentatoma (Euchistus) no evidence at all of 

 reductional division in the second mitosis. 



All maturation modes are then of the pseudomitotic type, and of 



