No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 1 35 



pears to be held by Grassi ('89). All these authors base their 

 conclusions solely on comparative anatomical data. 



Other observers, including Weismann ('66), Huxley ('77), 

 Uljanin, Kowalevsky ('73), Kraepelin ('72), Dewitz ('75) and 

 Cholodkovsky ('91^) regard the gonapophyses as homodynamous 

 with the true ambulatory appendages. Most of these authors 

 adduce support for their views from the origin of the ovipositor 

 during the larval and pupal stages. The ovipositor and sting 

 have been traced in Orthoptera and Hymenoptera to two pairs 

 of imaginal disks — one situated on the eighth, the other on the 

 ninth abdominal segment. On the latter segment the pair of 

 disks gives rise to a bifurcate or double pair of appendages. 

 (Dewitz, Kraepelin, etc.) But the mere fact that these append- 

 ages arise from imaginal disks is not sufficient evidence of their 

 homodynamy with ambulatory appendages, since the wings of 

 the Metabola also arise from imaginal disks, yet cannot belong 

 to the same category as the ambulatory appendages. The 

 imaginal disks of the gonapophyses must be traced into the 

 embryo and a connection clearly established between them and 

 the embryonic appendages, before the view advocated by 

 Huxley, Uljanin and others can be said to rest on a secure 

 foundation. XipJiidimn supplies this hitherto missing evidence. 

 In this form there can be no doubt concerning the direct con- 

 tinuity of the embryonic appendages with the gonapophyses. 

 One embryo which had just completed katatrepsis still showed 

 traces of all the abdominal appendages. The pairs on the 

 eighth, ninth and tenth segments were somewhat enlarged. 

 In immediately succeeding stages the appendages of the second 

 to sixth segments disappear ; the pair on the seventh disappear 

 somewhat later. Up to the time of hatching the gonapophyses 

 could be continuously traced, since in XipJiidmm there is no 

 flexure of the abdomen as in other forms to obscure the ventral 

 view of the terminal segments. From the time of hatching 

 Dewitz ('75) has traced the development of the ovipositor in 

 another Locustid {Locitsta viridissinid) so that now we have 

 the complete history of the organ. 



While there can be no doubt about the appendages of the 

 eighth and ninth segments, which go to form the two outer 



