No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 131 



(which in all probability are reduced ambulatory appendages) 

 a complete separation of the coelom into a lateral (diverticular) 

 and a dorsomedian (genital) portion does not take place, so 

 that the two cavities remain confluent. The portion of the 

 coelomic wall surrounding the proximal cavity joins the sexual- 

 gland while the diverticular (nephridial) portion acquires an 

 external opening, " which, however, is much nearer the middle 

 line than in the case of the anterior somites, and, indeed, may 

 be described as being common with that of the opposite side. 

 However this may be, the two openings soon become definitely 

 united to form a single opening, while the tubes themselves 

 persist as the generative ducts. Whether any large portion of 

 the latter are ectodermal in origin, that is to say, derived from 

 a growth of the lips of the opening at its first appearance, it is 

 impossible to say." 



If we accept Sedgwick's account it is easy to reduce the 

 genital ducts of insects to the type seen in Peripattts and con- 

 sequently to Annelid nephridia. In the first place, everything 

 goes to show that the appendage diverticula of the coelom are 

 homologous both in Peripatiis and Orthoptera. In both cases 

 the oviducts and deferent ducts arise from these diverticula by 

 partial constriction. Just as the ducts of Paipatiis run into 

 the cavities of the anal papillae, so the sexual ducts of Blatta 

 and Xiphidiiim run into the rudimental abdominal appendages. 

 In both cases there are terminal ampullae, for as such I venture 

 to regard the slight distal widening of the coelomic diverticula 

 in Sedgwick's Figs. 42 and 44. A comparison of these 

 figures with my Figs. 56 and 59 will show the close resem- 

 blance between insects and Peripatiis better than paragraphs 

 of description. 



As the exact limits of the ectodermal portions of the ducts 

 of Peripatiis have not been clearly ascertained, further com- 

 parison with the Insects cannot at present be undertaken. In 

 the Insecta only the vagina and ejaculatory ducts with their 

 respective accessory glands arise from the ectoderm. These 

 structures are median and unpaired in all insects except the 

 Ephemeridea, one of the oldest and most primitive groups. In 

 this group, as Palmen has shown ('84), the ducts of both sexes 



