124 WHEELER. [Vol. VIII. 



In his first paper ('9o) Heymons made the following state- 

 ment in regard to the genital ducts : " Von besonderer 

 Wichtigkeit scheint mir nun die Thatsache zu sein, dass 

 beim Mannchen der urspriinglich angelegte Ausfiihrungs- 

 gang nicht in seiner ganzen Lange zum Vas deferens wird, 

 sondern dass sich sein distaler Abschnitt spater wieder zu- 

 riickbildet, ohne je functioniert zu haben. Der wirklich als 

 Ausfiihrungsgang dienende Endtheil des Vas deferens, welcher 

 sich mit dem ectodermalen Ductus ejaculatorius verbindet, ent- 

 steht erst nachtraglich an dem urspriinglich angelegten Aus- 

 fiihrungsgang. Beim Weibchen dagegen bildet sich der ganze 

 primitive Ausfiihrungsgang zum Oviduct aus." 



This is the very opposite of what I have found : in Xiphidiuni 

 it is the male duct which at first occurs in both sexes in the 

 tenth abdominal segment — whereas in the female the oviducts 

 are an independent formation, the original male duct being 

 soon broken down. In the female both pairs of ducts are 

 established simultaneously since they are both coelomic 

 diverticula.^ 



In his more recent paper Heymons ('9i) describes the genital 

 ducts as terminating at the posterior edge of the seventh 

 abdominal segment. As he mentions this fact before he 

 comes to a description of the embryo with determinate sex, 

 I assume that he regards these ducts as common to both sexes. 

 What he saw was without doubt the pair of oviducts, not the 

 deferent ducts. From personal observation I can state that 

 the male ducts of Blatta end at first in terminal ampullae 

 enclosed by the appendages of the tenth abdominal segment 

 just as in XipJiidinm, whereas the female ducts terminate 

 in much flattened ampullae in the seventh segment. Whether 

 or not a rudimental male duct is present in the tenth segment 

 of the female Blatta embryo I have been unable to decide. 

 Perhaps Heymons found something of this kind and while 

 confounding the sex of the embryos he studied, was led to 

 make the above quoted remark. 



^ For the sake of greater exactness, I may state that the anterior pair is, perhaps, 

 formed a little sooner than the posterior pair, since the somites develop from 

 before backwards. 



