THE EMBRYOLOGY OF A TERMITE.i 



Eiitermes {R ippertii ?) . 



FIRST PAPER. 



(Including a contribution to the discussion as to the primitive type of development, and the 

 origin of embryonic membranes (amnion), and of the mesoderm, in the Insecta.) 



HENRY McELDERRY KNOWER. 



CONTENTS. 



Introduction i 



Technique 2 



General description of egg 3 



The yolk 6 



Segmentation and formation of the 



first rudiment of the embryo 7 



Origin of the mesoderm 16 



Origin of the amnio-serosal fold 18 



Growth of the amniotic and meso- 

 dermal rudiments 19 



Elongation of embryonic rudiment 



up to segmentation 21 



Changes in amnion and mesoderm 

 during this elongation 23 



Remaining development up to 

 hatching : 25 



General. 

 Conclusions as to the primitive na- 

 ture of this type of development.. 29 

 Origin of the mesoderm of insects .. 32 



Origin of the amnion of insects 36 



Explanatory note 53 



Bibliography 55 



Introduction. 



Though the Termites must be ranked among those insects 

 which have best preserved ancestral morphological traits, their 

 development has not been studied up to the present time. 

 Indeed, it is only within the last few years that we have been 

 enabled to judge of the details of development of any of the 

 primitive forms of insects. The technical difficulties which 

 the investigator of these forms must meet are very great, much 

 time being required to obtain few results, especially in dealing 



1 This paper was accepted as a thesis for the degree of Doctor of Philosophy 

 in the Johns Hopkins University, May, 1896. (See explanatory note at the end.) 



505 



