No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 139 



and this alone would suffice to distinguish it from the fat-body 

 which persists throughout life. 



It is perhaps premature to advance any hypothesis as to the 

 function and morphological significance of the suboesophageal 

 body, but I may call attention to its possible homology with an 

 organ in the Crustacea. The researches of Viallanes and St. 

 Remy go to show that the tritocerebral segment of insects is 

 homologous with the second antennary segment of Crustacea. 

 In the latter group of Arthropods this segment is provided 

 with the green-gland, a structure which develops from the 

 mesoderm and is generally regarded as a modified nephridium. 

 The suboesophageal body, providing it arises from the meso- 

 derm of the tritocerebral segment, may be all that remains 

 of this same pair of nephridia in the cephalic region of 

 insects. 



VIII. Technique. 



Xiphidhtm eggs, like those of other Orthoptera are not 

 easily sectioned in the younger stages, because their yolk 

 bodies are rendered so brittle by the hardening fluids and are 

 cemented together with so little protoplasm that they disin- 

 tegrate during the process of cutting. After the appearance 

 of the appendages the embryo may be readily dissected away 

 from the yolk either in the fresh or hardened &gg and mounted 

 or sectioned by itself. In the study of the envelopes, where 

 it is necessary to section the whole Qg^, the following method 

 gives fairly good results : — 



The eggs are taken from the galls and killed by being 

 placed for about a minute in water heated to 80° C.^ They 

 are then transferred for preservation to 70 per cent alcohol in 

 which they should remain for several weeks, if not months, in 

 order to allow the yolk to harden and to shrink away from the 

 chorion. The neglect of this simple precaution has led many 

 to exaggerate the difficulty of studying insect eggs or to 

 abandon them altogether. After remaining in the alcohol 

 for some time, the chorion may be removed by tearing it 



1 Alcoholic picrosulphuric acid also proved to be an excellent killing reagent. 



