No. 3-] THE EMBRYOLOGY OF A TERMITE. 533 



General Conclusions as to this Type of Insect 

 Development. 



Korschelt and Heider's recent text-book (17) contains an 

 argument for a modification of Will's and Wheeler's well-known 

 theory of a connection between the "invaginate," "immersed " 

 type of development exhibited by the Libellulids and some 

 Hemiptera, and the type followed by myriopods. 



On p. 775 (17) we find : "The invaginate type is best seen 

 in the Libellulids, which represent the direct connecting link 

 (Anschluss) with the phenomena exhibited by the myriopods, 

 and hence must be regarded as the more primitive type." 

 Again on p. 'jZ'j (17): "Wir haben oben gesehen dass bei den 

 Myriopoden bei fortschreitenden Langenwachsthum des Keim- 

 streifs derselbe in seiner Mitte eingeknickt und in das Innere 

 des Eies versenkt wird. In dieser Einsenkung, welche wir uns 

 zunachst durch das raumliche Missverhaltniss zwischen dem 

 langestreckten Keimstreif und der rundlichen Eiform ent- 

 standen zu denken haben, werden wir (wie dies schon Graber 

 andeutete und Will neuerdings ausfiihrlicher begriindet hat) 

 den Ausgangspunkt fur die Entwicklung des invaginirten 

 Keimstreifs der Libelluliden zu suchen haben. Wir werden 

 demnach fiir die Entwicklung des Insecten Keimstreifs die 

 Form der Invagination als die urspriingliche betrachten." 

 This account is apparently based on Heider's (13) discussion 

 of the subject in his monograph on Hydrophihcs. It is a 

 modification of Will's (27), also Wheeler's (25) theory, against 

 which in its original form Graber (9), in a more recent paper 

 than the one referred to before, brought forward strong 

 objections. 



Since the publication of the text-book of these two authori- 

 ties on insect embryology, further investigation has shown, 

 that besides Oecanthus which is mentioned in it, a number of 

 Orthoptera, as well as the Termite (which is strikingly orthop- 

 teran), exhibit developmental phenomena similar to those of the 

 Libellulids. It now seems evident that there are no grounds 

 whatever for regarding the method of development followed by 

 this latter group as at all more primitive than that observed for 



