NUCLEOLI IN EUSCHISTUS VARIOLARIUS. 23! 



characteristic of the second division as it is of the first, although, 

 as we have already pointed out, there are exceptions to this rule. 

 There can be no possible doubt of our identification of these 

 groups as second spindles, because they are invariably found in 

 regions of the testis surrounded by spermatids in different stages 

 of development and, further, the form of the chromosomes is so 

 beautifully demonstrated in our smear preparations, it is hardly 

 possible to confound the first and second spindles, 1 a mistake 

 easily made in sections. That the individual chromosomes may 

 change their relative positions at this stage, while the form of 

 the group remains unchanged, is a possibility that any observer 

 would naturally consider. But as we find in our preparations, 

 the ring-like grouping of the chromosomes of the first spindle 

 so constantly duplicated in the second spindle, with the micro- 

 chromosome (the one chromosome that can be identified beyond 

 question) maintaining its characteristic position in the center of 

 the ring, the identification of the eccentric chromosome of both 

 spindles as probably the same chromosome, is certainly as legiti- 

 mate a conclusion, as forcing an arbitrary contradiction of this 

 assumption, in order to support a theory. 



In complete opposition to what Wilson calls his "demonstrative . 

 evidence " on this point, we refer to our published photographs, 

 Plate III. (in the paper quoted above), 29, 32, 33, 34, 35, 36, 

 37, 40, 41, 43, showing polar views of late anaphases or telo- 

 phases of second spindles, in which every chromosome of each 

 daughter plate can be counted. In all these preparations there is 

 an eccentric, lagging in most cases dyad - - chromosome, but as 

 ten chromosomes can be clearly counted at each pole, we fail to 

 see how the situation is improved, for Wilson to claim, that where 

 the lagging chromosome divides in this spindle it is not to be 

 identified with the " odd " chromosome which he says, " is, in 

 such cases, akvays to be found elsewhere in the group'' We have 

 given demonstrative evidence that this is not so in our preparations. 



The essential fact is not the relative position of the accessory 

 chromosome in either the first or second spindles, but whether 



1 The ring-like grouping of the chromosomes is also characteristic of the first and 

 second spindles of Euschistus variolarius, where the distribution of the unequal 

 tetrad in the second spindle adds conclusive proof of the identity of the spindles. 



