344 THE GROUSE IN HEALTH AND IN DISEASE 



seminis, which runs across the proglottis and then turns backward ; in some 

 preparations this turn is seen " en face," and then the radiating muscles give the 

 appearance of a ring of very fine spines, and, indeed, at first I thought that there 

 was such a ring, but I believe the above is the true explanation. There are three 

 testes, the vasa deferentia of which unite, and after entering the cirrus-bulb enlarge 

 to form a vesicula seminalis. The vagina opens ventral to the penis. The uterus 

 is a single chamber unbranched. It forms a conspicuous feature in the hinder end 

 of stained specimens. At first it appears as a spherical organ lying in the middle 

 line at the hinder end of each proglottis, but as it grows and absorbs more of the 

 parenchyma it tends to become triangular or square, but always with very rounded 

 angles. It contains a large number of relatively large onchospheres or tape- 

 worm-embryos (PI. LI., Fig. '7). According to Wolffhiigel, the embryos measure 

 0'02 mm. in breadth by 0'04 mm. in length. The typical six embryonic hooks 

 are very characteristic. The partners in each pair, for instance, are usually widely 

 divaricated ; their length is 0'014 mm. These characteristic Hymenolepis ova 

 have three envelopes : the innermost, closely applied to the embryo, is never 

 produced into horns ; between it and the middle envelope is only a clear fluid in 

 which the embryo floats ; between the middle and the outer envelope are the much 

 vacuolated remains of cells. The position of the embryo is eccentric with regard 

 to this outer shell, which measures 0'073 mm. by 0'066 mm. The measurements 

 are again Wolffhugel's. 



We have no information about the fate of these embryos, but as a general rule 

 the cystic form of this genus lives in some insect or myriapod, as is shown by the 

 fact that this genus of tapeworm occurs in bats, insectivores, Rodents, and insecti- 

 vorous birds. Hymenolepis nana occurs in man, most frequently in children, and 

 is not at all uncommon in Italy. Sporadic cases of H. diminuta occurring in man 

 are also recorded. 



'We have made laborious investigations to try and discover this second 

 host. In searching for the cysts of the tapeworms we began with the insects 

 which occurred most commonly in the crop of the Grouse. These we examined 

 microscopically, both after teasing the body up in glycerine and by grinding 

 it up but not too finely in a mortar ; in some cases also, as Mr Fryer * has 

 recorded, sections were made and examined, but always without result. 



We were at two disadvantages in hunting for the cysts : firstly, we did not 



1 Interim Report of the " Grouse Disease " Inquiry. 



