6 



SOME ASPECTS OF MORPHOLOGY 



rudiments, and a smaller posterior part, which comes to lie at the 

 sides of the epipharynx. Cavities of doubtful significance may 

 appear in both these mesoderm masses, but, Eastham remarks, they 

 are so irregular and so unlike those of the well-defined somites of 

 the body that it is doubtful whether they have any metameric 

 importance. This author, in discussing the general problem of 





n. 



ow 



Pr'A . coel. 



Fig. 2. A. Anterior extremity of an embryo of the Stick Insect, 

 Carausius morosus, showing rudiments of developing appendages. 

 A, antenna ; H, hypopharynx ; L, labrum ; Md, mandible ; 

 Mci', maxilla ; Pr.A, pre-antenna. B. Transverse section across 

 a similar embryo, passing through the pre-antennal rudiments 

 (PrA). PrA.coel, pre-antennal coelom sac ; S, stomodaeum ; 

 Yl, layer of yolk cells. (From Wiesmann.) 



head-segmentation, supports the established opinion that six 

 somites are involved, but concludes that the paired labral rudiments 

 represent the appendages of the protocerebral segment. Very 

 recently the occurrence of coelom sacs in close association with 

 paired labral rudiments has been described and figured in two 

 other insects : viz., by Mellanby (1936) in the Reduviid bug 

 Rhodnius prolixus and by Roonwal (1937) in the African Migratory 

 Locust (Locusta migratoria, subsp. migratorioides, Fig. 3). Both 



