NEW AVIAN TAPEWORM. 203 



The testes of Otiditomia (text-fig. 24, p. 201) form, in fact, a very 

 compact mass, which ahiiost suggests ;i single organ wliose com- 

 pactness and geneial cliaracters form a very distinguisliing m;irk 

 of this genus. In the sagittal sections ah-eady referi-ed to, the 

 mass of testes is seen to form a hand rather lenticular in outline, 

 i. e. tapering dorsally and ventrally, which extends without inter- 

 mission from the dorsal to the ventral muscular hody-wall. In 

 transverse sections of the worm the testicular mass is seen equally 

 well to form an unbroken dorso- ventral layer occupying the 

 whole of the central paienchyma between the lai^ger ventral water 

 vascular vessels, to the outside of which the testes do not extend. 

 The wall of testes which thus exists — marking, as has already 

 been said, the posterior region of the proglottid — is a very thin 

 one. It is formed of only a single layer or in parts of two layers 

 of testes. 



In their general form the testes are oval. The very small 

 amount of space occupied by the testes in an antero-posterioi- 

 plane is striking ; but it is greater in the less fully than in the 

 more fully mature proglottids. In the former the antero-posterior 

 diameter of the group of testes is a little more than one-third of 

 the length of the segment ; in the latter peihaps one-tenth, and 

 the disproportion becomes even gi-eater in absolutely ripe seg- 

 ments, where, indeed, the testes finally disappear, being apparently 

 pressed out of existence by the swelling pi-oglottids. 



In such tapeworms as I am acquainted witli by first-hand 

 knowledge the testes are scattered in the medullary parenchyma, 

 though often closely adpressed ; but there is no particular modi- 

 fication of the medullary parenchyma in the region occupied by 

 the testes. The same conditions appeal* to obtain in many foims 

 described by others. 



In Otidita'nia, howevei-, the testes lie in a very distinct cavity, 

 which has in sagittal sections of the entire proglottid a lenticular 

 outline already mentioned. This cavity is not everywhere apparent 

 as actual spaces lying outside of the testes ; it is for the most part 

 filled up with an interstitial tissue, which separates the individual 

 testes and in which they lie closely packed together. Although 

 this interstitial tissue is not veiy different in appeai\ance from 

 the medullary parenchyma, it is separated from it by a distinct 

 boundary-line and is more faintly stained by carmine, and does 

 not seem to contain any calcareous corpuscles. The distinctness 

 of the mass of testes, as a whole, from the suirounding i-egions 

 of the proglottid will be apparent fi-om text-figure 26 (p. 204). 

 Here and there the interstitial tissue seems to be replaced by 

 actual cavities which contain no fluid that takes a stain. They 

 appear, in fact, to be empty. 



Since the testes lie quite posteriorly in the segments, it is 

 obvious that they must be close to the transverse vessels of the 

 water vascular system, which unite the vential vessels. The 

 spaces to which I have referred, I believe, entirely belong to 

 the transverse watei" vascular trunks which are large in the 



