NO. 2040. NOTES ON A VIVIPAROUS DISTOME— LINTON. 553 



opposite, each lying between the median line and a ramus of the 

 intestine. Cirrus short and spinous, surrounded by compact prostate. 

 There is a small seminal vesicle on the postero-dorsal border of the 

 ventral sucker from which a duct leads along the dorsal side of the 

 sucker to the genital aperture. Ovary median, situated in front of 

 testes and separated from them about as far as the diameter of a 

 single testis, or a little less, oval, the transverse diameter 'greater 

 than the axial diameter in my specimens. The vitellaria consist of 

 two rather narrow rows of subglobular masses which extend from 

 near the postero-lateral border of the ventral sucker nearly to the 

 testes. Along the margins of the neck and body of living specimens 

 which had been flattened under the cover glass numerous long- 

 pyriform cells were seen (fig. 8). These are probably yolk-forming 

 cells. The uterus is very voluminous, its folds occupying practically 

 all the space between the testes and the ventral sucker and reaching 

 nearly to the lateral margins of the body. It passes along the dorsal 

 side of the ventral sucker to the right of the prostate and enters the 

 ejaculatory duct from the antero-lateral side. In some cases ciliated 

 larv£e (miracidia) and eggs were clustered on the right side of the 

 genital aperture in the uterus (metraterm) (fig. 4m) . The ova in the 

 anterior half of the uterus have transparent walls and contain ciliated 

 larvae. These are readily recognized both in living and mounted 

 specimens by the conspicuous spot of black pigment which is easily 

 seen through the body wall. The posterior folds of the uterus are 

 filled with reddish-brown ova in which larvae have not yet developed. 

 These ova are smaller than those in the anterior folds and the 

 shells are thicker. Along with ova containing larvae in the anterior 

 folds of the uterus are miracidia which have escaped from their 

 shells. In the living specimens they can be seen through the body 

 wall moving about slowly in the uterus by means of their cilia. 

 When they are removed from the uterus they retain their activity 

 for but a short time in sea water, the cilia soon taking on a bristle- 

 like appearance. The cilia cover the entire surface, being a little 

 longer at the posterior end than elsewhere and most dense at the 

 anterior end. The ciliated cells are relatively large and have rather 

 large nuclei. Miracidia lying free in sea water measured from 0.12 

 to 0.16 millimeter in length and 0.08 millimeter in breadth. These 

 measurements do not include the cilia, which aie about 0.02 milli- 

 meter in length. 



My attention was called to an interesting feature of these miracidia 

 by my friend Doctor Coe, who chanced to be at the laboratory at the 

 time that I was examining these dis tomes. Each of the ciliated 

 larvae was found to contain a single redia. These can also be made 

 out not only in sections but in whole mounts stained with carmine. 

 In all the living specimens observed the anterior end of the redia was 



