FROM MAMMOTH CAVE. 139 



A very large, pale green, tabulated gland which over- 

 lies the ventriculus is very conspicuous. It appears to be 

 the salivary gland. From its anterior extremities, oppo- 

 site the beginning of the ventriculus, two large contorted 

 ducts extend forward with the oesophagus. They continue 

 separate until within the epicranium, and seem finally to 

 unite at a median opening in the floor of the mouth. The 

 glands probably secrete a slime, which was noticed in the 

 wake of living individuals. Similar glands occur in Sciara 

 and Chironomus larvae, but are of a brown color, and the 

 ducts are short. Larvae of these genera have in addition 

 to the glands a pair of salivary vesicles which overlie the 

 brain, and send their ducts forward towards the mouth. 

 No such vesicles are present in the Mammoth Cave larvae. 



RESPIRATORY AND CIRCULATORY SYSTEMS. 



I have been unable to find any trace of spiracles or 

 tracheae in either Sciara or the Cave larvae, and conclude 

 that respiration is effected at the general surface. If 

 present the dorsal vessel must be of extreme delicacy. I 

 have seen nothing of it. 



SUMMARY. 



The features of structure to which especial attention is 

 directed are the following, numbers 1-4 of which the cave 

 larvae possess in common with larval Sciara : 



1. The imperfect epicranium, the head being probably 

 represented in part by the segment which follows. 2. 

 The location of the brain. 3. The absence of stigmata 

 and tracheae. 4. The great development of the salivary 

 glands. 5. The proboscis-like labrum. 6. The large 

 ocelli with small eye-spots beneath them. 7. The absence 

 of salivary vesicles. 8. The great length of the oesoph- 

 agus and salivary ducts. 9. The green color of the sali- 

 vary gland. 10. The segmentation and folding of the 



