346 ANIMAL PARASITES. 



anterior and posterior ends of the canal ending caecally during 

 the stage of Trichinal existence ; in both, the sexual orifices must 

 be subsequently produced by an external dehiscence of the tissue. 

 The future funiculus spermatid^ and testis grow at the anterior 

 caeca! extremity distinctly over to the other side of the intestine, 

 and here always terminate csecallv: the other, ready-formed branch 

 of this apparatus dehisces towards the walls of the intestine, a 

 little way from the extremity of the abdomen, so that, from this 

 point, the male seminiferous organs and the intestinal canal form 

 a cloaca with a common orifice. 



The foundations of the female genitalia are similar. Here, 

 also, the anterior crecal tube passes over to the other side, 

 and reaches the neighbourhood of the chitinous lateral wall. 

 At this point the canal must dehisce simultaneously with the in- 

 tegument also at the level of the anterior part of the stomach, or 

 but a little way behind it. The other end of the caecal tube, 

 which is near the extremity of the abdomen, also bends over to 

 the other side, and runs forward, whilst between these parts all 

 sorts of convolutions grow out, and lastly the ovary, the uterus, 

 and the vagina are formed from them. At no period of Trichinal 

 existence does this tube open outwards, but the Trichina exhibits 

 only a single orifice at the extremity of the abdomen, namely, 

 that of the anus. The complete, distinct fusion of the organs in 

 question could certainly only happen at that period of the life of 

 the animal when it had arrived in a place (in an intestine) 

 adapted for its further development, and in which, consequently, 

 the formation of the genitalia is completed. As I cannot think, 

 even from the teleological grounds above stated, that the Trichina 

 are only male individuals, we must assume that the tube referred 

 to may subsequently become developed and converted in the way 

 described by me into the internal sexual organs of both sexes, 

 and afterwards form any sexual organs which may still be wanting, 

 and that, therefore, it is almost impossible to determine, during 

 the Trichinal existence, to which of the two sexes the mature 

 animal would belong. Therefore, I agree with those authors who 

 regard this tube as the primitive foundation of the sexual organs 

 in general. 



The abdominal extremity of the worm, that is to say, its 

 thicker portion, is perforated in its middle by the anus, into 

 which the above-described intestine directly passes. Luschka 

 says " that, at the extremity of the abdomen, we find three dark 



