222 KATHARINE FOOT AND E. C. STROBELL. 



kappenformige Masse einem grossen Plasmosom aufgelagert er- 

 scheint, eine auserordentliche Ahnlichkeit mit den Befunden in 

 den Keimblaschen des Lam'ellibranchiaten-Typuszeigen, d. h. in 

 denjenigen Keimblassen, in welchen sich zweierlei Nucleolen von 

 verschiedener Lichtbrechung, Quellbarkeit und Tingierbarkeit 

 befinden." 



It is a suggestive fact that in Allolobophora we have an her- 

 maphrodite form, and if one is determined to regard the chromatin 

 nucleolus of the spermatocytes as a sex-determinant, some inter- 

 esting conclusions might be drawn from a comparison of the two 

 types of nucleoli observed in this hermaphrodite form, with the 

 two types characteristic of the male and female cells in Euschistus. 

 Compare for example the large nucleolus in the germinal vesicle 

 of Allolobophora (Photo 31) with the large achromatic nucleolus 

 of the germinal vesicles of Euschistus (Photos 1 8 to 30), and com- 

 pare further the smaller chromatin nucleolus of Allolobophora 

 (Photos 31 and 32) with the chromatin nucleolus of the sperma- 

 tocytes of Euschistus (Photos i to 10). 



Even if we could be sure that in Euschistus the achromatic 

 nucleolus of the egg cells is not represented in the male cells, and 

 that a striking likeness exists between the male and female nu- 

 cleoli of Euschistus and the two types of nucleoli in the germinal 

 vesicles of Allolobophora, we would still be unable to claim from 

 the comparison any results of general significance, for the reason 

 that the observations of many investigators of the spennato- 

 genesis of insects offer contradictions to an assumption that the 

 achromatic nucleolus is associated solely with the female cell 

 these observers having figured a pale, achromatic nucleolus 

 in the spermatocytes, in addition to the chromatic nucleus char- 

 acteristic of these cells. As opposed to these facts, however, 

 other investigators have found no structure in the spermatocytes 

 that can be interpreted as a nucleolus, other than the character- 

 istic chromatin nucleolus. 1 These conflicting observations, if 

 equally reliable, compel the conclusion that individual forms may 

 differ as to the absence or presence of an achromatic nucleolus. 



1 In his " Studies on Chromosomes IV.," Jour. Exp. Zool., Vol. VI., No. i, 

 1909, Wilson in describing Syromastes, does not mention a large pale plasrnosome, 

 such as he has described in other forms. In Pyrrochoris he states that there are from 

 one to three nucleolar-like bodies, which on account of the staining reactions, he 

 believes to be plasmosomes, page 82. 



