234 On certain, Species of the Genus Demodex, Oiven. 



pointed. Spines on dorsal surface of capituluni quite long 

 and pointed at the end. Cephalothorax fairly wide. Tliere 

 is an internal chitinous structure in one of the specimens 

 which seems to be a penis; it is shaped as figured (text- 

 fig. 2 a). 



Besides a few adult specimens, I have been able to mount 

 and examine two examples of a much more elongated form, 

 which is apparently a nymph (although very much larger 

 than any adults of this species so far collected, no traces of 

 the fjenital opening can be detected). The body (including 

 capituluni) of this nymphal form is about seven and a half- 

 times as long as the width of the cephalothorax. Its abdo- 

 men is rather more than two and a half times the lencrth of 



o 



Fio-. 2. 



Demodex musculi, Oudms. a, penis ; b, dorsal view of capituluni. 



the cephalothorax + the capituluni. PI. IX. fig. 2, gives a 

 good idea of the appearance of this elongated form, but the 

 length is shown a little too short. The legs are rudimentary 

 in this nymph, and their structure is difficult to ascertain 

 with certainty; there are also four pairs of small rounded 

 structures near the middle line, which are, perhaps, the basal 

 segments of the developing legs of the adult. 



Measurements. — ? . Length of body (including capituluni) 

 150 /A ; width of cephalothorax 22-38 ix. Length of body 

 of S 125 yu., of large nymphal form 235 fi ; width of cephalo- 

 thorax 30 /A. 



Material. — Four tame mice were examined, and the Demo- 

 dex was discovered in three of them, but the parasites were 

 very few in number. 



