30 JOHN E. GUTBERLET 



usually a large number of free proglottids. If they did not remain 

 in the intestine for a considerable length of time there would not 

 be nearly as many. Further proof is furnished by the fact that the 

 free proglottids have embryos which are mature, showing the oncho- 

 spheric characteristics, while the oldest segments that are still at- 

 tached to the worm have embryos that are not entirely mature. 

 This same condition has been observed in Davainca proglottina as 

 Blanchard (1891:435) states that the oldest proglottids separate 

 from the others and remain in the intestine to become mature be- 

 fore passing out. The proglottids do not always separate from the 

 worm singly, but may drop off in groups of three or four. 



The fact that the proglottids separate from the worm before 

 they are entirely mature is one of great importance in taking up 

 experimental work for infection of intermediate hosts. If the em- 

 bryos are fed to insects or other invertebrates before they are ma- 

 ture they will be digested, and thus infection cannot be produced. 



B. CYSTICERCUS 



The cysticercus of Choanotcenia infundibiiliformis was found 

 in the abdominal region of the body cavity in the common house 

 fly, Mnsca domestica. The flies had been fed on embryos from 

 ripe proglottids of this species of worm, and at the end of twelve 

 days were killed. The cysticerci appear to be nearly ripe or ready 

 for transmission into the adult host. The time for the develop- 

 ment of the cysticercoid varies with different species and under 

 different conditions. Grassi and Rovelli (1892:85) found that 

 Davainea proglottina developed from the onchosphere into a ripe 

 cysticercus in less than twenty days. Schmidt (1894:9) found that 

 the development of the cysticercoid of Drepanidotcrnia anatina 

 (Krabbe) varied with the time of the year and the influence of the 

 temperature. In the summer the embryo developed in an ostracod, 

 Cypris ovata, into ripe cysticercoids in two weeks. 



The cyst proper (Figs. 11, 12, c) containing the scolex is oval 

 in shape, 220/i, long and 120/x in diameter. 



The bladder (Fig. 12, h) ov tail, which is also oval in shape, 

 is located against one side of the cyst and is somewhat flattened on 

 that side. It is 220 to 2v30/x long and from 116 to 120/t in breadth. 



