No. 3.] CLINOSTOMUM HETEROSTOMUM. 705 



eating with the lateral vessels running to a caudal vesicle ; 

 the white is due to granules of calcium carbonate, as it is 

 removed by immersing in acetic acid. Generative apparatus is 

 undeveloped. 



On comparing the descriptions of these two forms, they are 

 seen to differ in no respect whatever, unless it be in their hosts, 

 which are still very similar. 



Although I have not the type specimens for comparison, the 

 description given by Looss (13) of Distomuni reticulatwn found 

 encapsulated in the musculature of Stlitnis giants, for which 

 we have also the synonym D. dictyotus (Monticelli, '93)^ applies so 

 exactly in every particular to the forms we have just considered, 

 that I have not the least hesitation in concluding that they 

 are the same. Indeed, this identity has been pointed out by 

 Leuckart (14), who considers it one with Leidy's Clmostomum 

 gracile. 



The other specimens before me are identical forms, although 

 none are definitely diagnosticated except those labeled by Stiles 

 and Hassall, Clinostotmwi heterostomuni. In short, there seems 

 to me to be no doubt that all the specimens are individuals of 

 one and the same form, and that that form is in reality a devel- 

 opmental stage of D. heterostomimi. 



My own observations on these specimens give the following 

 additional points. 



There is a slight variation in the stage of development of the 

 different specimens, as may be judged from the differences in 

 the maturity of the genital organs, but in all the two testes may 

 be discerned with the ovary lying between them (PL XXXIX, 

 Fig. 7), beside the coils of the very immature uterus. The 

 lumen of the portion of the uterine tube running forward is 

 quite narrow in proportion to the thick layer of deeply staining 

 cells which surrounds it. Anteriorly it bends on itself, and 

 enters the sac described in D. Iieterosto^mim, which is here a 

 long, narrow, empty sac whose walls, furnished like the uterus 

 with a thick layer of cellular tissue, seem relatively very thick. 

 The cirrus is still very immature, although in one of my speci- 

 mens (that from the pectoral muscle of the frog) the differen- 

 tiation of its parts is fairly complete. 



