452 E. A. MINCHIN ON SOME DETAILS IN THE ANATOMY OF 



respect to the salivary glands must be related to the difference in 

 their habits. The adult flea, I need not say, is a blood-sucker, 

 and in blood-sucking insects generally the function of the salivary 

 glands is believed to be that of producing a secretion which is 

 mixed with the ingested blood and prevents it from coagulating. 

 Incidentally the salivary glands of the adult flea, if crushed and 

 examined, can be seen to contain many yeast-like bodies of several 

 kinds, and it is supposed that it is these microbes which are 

 responsible for the local irritation and itching caused by the 

 puncture of the flea's proboscis. The flea-larva, on the other 

 hand, is more or less omnivorous, but appears to feed principally 

 on the faeces of the rat, as well as dirt and debris of all kinds. 

 Consequently its salivary glands have a function in the insect's 

 economy entirely different from that of the adult flea, assisting 

 probably in the digestion of the food, and their larger size in the 

 larva indicates a greater secretive activity than in the adult. 



III. The Male Reproductive Organs. 



The genitalia of the male flea exhibit a singular complication 

 of parts and of their arrangement, but are nevertheless very easy 

 to dissect out, and with a little care the entire reproductive system, 

 from testes to penis, can be mounted as one preparation, in which 

 every detail can be studied with the exception of those minuter 

 points of structure which require sections for exact study. 



A general sketch of the various parts is given in Plate 28. 

 All the details of this sketch have been drawn from mounted 

 dissections with the camera lucida at a magnification of 150 

 diameters, reduced in the reproduction by one-half. At the same 

 time the relation of the various parts and their relative position 

 in the body has been checked by sketches of the whole system, 

 both of such parts of it as can be seen through the body-wall of 

 the flea without dissection, and also as it is seen when the abdomen 

 of the flea is freshly opened with the least possible disturbance of 

 the organs. 



Most anteriorly are situated the two conspicuous testes (T , T.) 

 with their ducts coming off from them, and shaped somewhat like 

 a pear would be if the stalk (the duct) came off from its thicker 

 end. The testes lie dorsal to the stomach, but vary to some 

 extent both in size and arrangement. When the testes are of 

 large size, as in the younger males, they lie one in front of the 



