TWO Si'liClES OF CYSTICKRCalDS. 11 



For tliis purpose a litter of young rats was separated froui tlieir 

 mother as early as possible and isolated. They were fed entirely 

 on boiled bread and milk. They were kept under observation 

 for three months, during which time frequent examination of 

 their faeces showed that they were free from tapeworms. Two of 

 the rats were then fed daily with the fleas, which were mashed up 

 in their food. This was continued for 19 days, feeding being 

 omitted on three of these, when one of the rats died. During 

 this period the faeces were examined regularly, but no ova were 

 found. On examining the dead rat, five specimens of Hymenolejns 

 dlminuta were found in the intestine. They wei'e of various 

 sizes, the largest being over 40 cm. long and the smallest only 

 1 cm. Next day numerous ova were found in the fasces of the 

 other rat. From this it was evident that the complete develop- 

 ment of Hymenoleijis diminuta took place in less than three 

 weeks. Grassi and Rovelli found ova after 15 days, which was 

 probably about the actual length of time required. The remaining 

 rats of the litter were kept under observation for a further period 

 of two months, but during that time no ova were found in the 

 faeces of any of them. The same experiment was repeated later 

 with a similar result, ova appearing in the faeces on the 19th day. 

 The rat which survived the first experiment was eventually 

 killed and nine tapeworms were removed from its intestine. A 

 total of 14 tapeworms was therefore pi'oduced from the 340 fleas 

 with which the rats had been fed. This indicates that about 

 four per cent, of the fleas contained Cysticercoids, and the result 

 agrees with the number of Cysticercoids found in fleas which were 

 actually dissected. 



The supposition, put forward in the previous communication, 

 that the flea becomes infected in its larval state, had to some 

 extent been confirmed. The intact ova of Hyvienolepis diminuta 

 were found in the intestines of 2 larvae out of 145 examined. No 

 stages in the development of the Cysticei"coid, however, had been 

 yet met with in the larval flea. On the other hand, a very young 

 Cysticercoid had been found in the body-cavity of one out of a 

 dozen pupae examined. The presumption was that it was only 

 the oldest and largest flea-larvas that were capable of ingesting 

 the tapeworm eggs and that no development took place until the 

 beginning of the pupal stage. 



The second Cysticercoid (text-flg. 2, p. 12) was of much greater 

 interest than the first. Hitherto only a single specimen had 

 been met with, and it occurred in the body- cavity of a male 

 Cercdophyllus fasciatus. It was considerably smaller than the 

 first Cysticercoid, and like it consisted of an oval body and a tail. 

 The former was "16 mm. long and the latter '19 mm. The two 

 outermost layers of the body-wall were the same as before, 

 but the parenchjmiatous and fibrous layers were not so sharply 

 differentiated from each other. The scolex, again, was very much 

 larger (diam. '096 mm.) and it had a rostellum armed with a 

 single row of spines, OS' in number. The length of each spine was 



