STRUCTURE AND DEVELOPMENT OF EMBIA TEXANA. I I I 



segment of the abdomen. Its walls consists of columnar epithe- 

 lium short uniform cylindrical cells in the larva and elongate, 

 more or less pear-shapecl, irregular, secreting cells in the adult. 

 The muscular layer surrounding the mid-gut is much reduced, 

 and the chitinous lining of the fore-gut is wanting in this portion. 

 At the base of the Malpighian tubules the wall of the mid-intes- 

 tine is thickened, forming the gastro-ileal valve. Here, in a con- 

 ical chamber formed just beyond the valve, commences the cuticle 

 from the proctodaeal invagination, but unlike the oesophageal 

 chitin, it is thin, replicated and smooth. The ilium is normally 

 much contorted, but when filled with food can be straightened. 

 Its numerous circular muscles then force it tense and crowd the 

 mid-gut into the thorax. The globular rectum fills out the last 

 two segments of the abdomen. When not evacuated it is filled 

 with rasped wood and other fragments of vegetable origin. Its 

 walls are strongly bulged by the six large cushion-like rectal 

 glands which consist of long convoluted secreting (?) cells each 

 with a large central nucleus. The Malpighian tubules vary in 

 number with the age of the individual, becoming about twenty- 

 four in the adult. In the younger stages they are rather shorter 

 and thicker with their nuclei more aggregated, /. e., their cells are 

 smaller. Their cells frequently present a honey-combed struc- 

 ture, probably due to the solution of their contents in the re- 

 agents for clearing. 



The heart of Eni^ia can be distinctly seen through the overly- 

 ing translucent chitin, extending the length of the body. Even 

 when pigmentation is greatest the heart is still evidently visible 

 from above. The blood corpuscles are large and elliptical. 



The suprarjesophageal ganglion (brain) of the nervous system 

 is relatively small ; the optic lobes send off a stouter nerve to the 

 eyes than is apparently the case in Professor Grassi's species. 

 This may be in part due to a difference in the power of sight in 

 the two species. The deutocerebrum is flattened, the antennal 

 nerves very slender, an innervation that might be expected for 

 organs of so poor sensory development. Owing to the absence 

 of ocelli there are naturally no ocellar nerves. The suboesoph- 

 ageal ganglion is comparatively large, sending an anterior nerve 

 in front of the cesophageal commissures. The remainder of the 



