2O6 MAULSBY W. BLACKMAN. 



The results of Wilcox, '95, '96 {Caloptenus}, and de Sinety, 

 '01 (Orthoptera), however, are indeed radically different. Even 

 here, however, I believe that the divergence is due either to the 

 authors' interpretation of observations, or to insufficient or infe- 

 rior material. Wilcox asserts that the two spermatocyte mitoses 

 accomplish a double transverse division of the chromosomes. 

 Such is not the case in the western individuals of the same species 

 where a longitudinal, followed by a transverse, division invariably 

 occurs. De Sinety, working upon the cells of several genera of 

 Orthoptera, asserts that the two divisions are longitudinal. This 

 also appears to be a mistaken conception, as pointed out by 

 McClung, '02. Appearances which upon superficial examination 

 might lead to this view are occasionally met with in Orthopteran 

 material, but when studied closely a different interpretation must 

 always follow. In Scolopcndra spermatocytes I believe it would 

 be impossible to arrive at this conclusion however strong a pre- 

 conception the observer may have had. The tetrad figures 

 accompanying this article can by no possibility be logically inter- 

 preted as representing anything but a longitudinal and transverse 

 division of the chromosomes. In the interpretation of the first 

 spermatocyte chromosomes and in the sequence of the succeed- 

 ing divisions I am gratified to note that P. Bouin, working upon 

 other genera of Myriapoda, agrees with my conclusions upon 

 Scolopendra. 



The tetrad forms which are of most common occurrence in the 

 arthropods are modifications of the cross, double V and ring 

 figures found in Anasa (Paulmier, '98) and Hippisais (McClung, 

 'oo). It is very probable that all of the other tetrads found in 

 this group are obtained by a greater or less modification of the 

 same process. Such is evidently the case in Copepoda (Ruckert, 

 '94) (Hacker, '95) ; in Gryllotalpa (Vom Rath, '91) and seems 

 also to be true of other invertebrates, TJialasseina and ZirpJiea 

 (Griffin, '95), Unio (Lillie, '95), etc. 



The typical arthropod tetrad as exhibited in the Insecta, 

 and in the Myriapoda is obtained in the following manner : 

 The chromatin segments of the matured number as they arise 

 from the spireme stage (Insecta) or from the aggregated seg- 

 ments in the karyosphere (Myriapoda) are long slender threads 



