457] PSEUDOPHYLLIDEA FROM FISHES— COOPER 169 



much contracted longitudinally. There the largest uterus-sac measured 

 0.8mm. wide by 0.67 long, while the width of the proglottis in question was, 

 at the posterior borders of the spurious articulations, 1.57mm. In fairly re- 

 laxed strobilas it increases in dimensions from 0.18 by 0.14mm., where the first 

 eggs appear in the lumen, to 0.87mm. long by 0.48mm. wide, where the proglot- 

 tis is 0.80mm. wide at its middle, in the latter case, of course, pressing against 

 the dorsal and ventral walls even as far as the cuticula. From a comparison 

 of these measurements, and the further fact that in the case of the former 

 much contracted strobilas there often appears, behind the region showing 

 the nearly obhterated genitaha, a more relaxed one in which the relations of 

 the uterus-sac to the other organs is quite as in the competely relaxed strobilas, 

 one is inclined to conclude that the characters of the family above quoted 

 apply to this species only in the case of proglottides much contracted longitu- 

 dinally. In the quadrate proglottides the smaller, that is, younger sacs alter- 

 nate irregvilarly from right to left, as do the uterine openings, and according 

 as the cirrus pouch and the vas deferens in particular (on account of its above- 

 mentioned position) occupy the opposite sides of the proglottis. Externally, 

 in alcohohc specimens, the uteri appear as a gradually enlarging series of brown 

 punctations caused by the contained eggs showing through the thiimed body 

 wall, as pointed out originally by Rudolphi and other writers. 



The wall of the uterus consists of a thin membrane on the inside of which 

 a very few scattered and somewhat flattened nuclei indicate its original epi- 

 thelial nature. In young proglottides, where no eggs are to be seen in the 

 small uterine cavities, the wall is composed of an epithehum about 8/i thick, 

 showing prominent nuclei but no distinct cell-boundaries. Furthermore 

 in such early stages the lumina of the uterine ducts, developing in the manner 

 described by Young (1913) and Shaefer (1913)^ are not completely formed nor 

 in connection with the cavities of the sacs, but the uterine apertures are promi- 

 nent. In the first two or three sections of a lOn frontal series, taken from 

 the ventral surface, they appear as distinct somewhat elliptical apertures 

 about 26m in transverse diameter, but in the third or fourth section are closed, 

 only to reopen as the cavity of the uterus-sac, thus showing that the membrane 

 closing the aperture is only about 10^ in thickness. And this closed condition 

 is maintained until the uterus-sac attains the above-mentioned maximum 

 size and becomes greatly distended with eggs. Then the functional opening 

 is estabUshed by the rupture of the membrane which has meanwhile reached 

 a length of 0.046 to 0.058mm. by a width of 0.034 to 0.046, its elliptical outhne 

 thus having been retained. The opening does not become as regular in outhne, 

 however, as the membrane, for the latter remains around the rim as ragged 

 processes, which render the determination of the exact location of the aperture 

 in toto mounts a matter of no little difficulty. The uterus openmg is sur- 

 rounded by a series of radiating cells like those of the opening of B. scorpli 

 described above. 



The fresh eggs examined in saline solution are elliptical to ovoid in shape, 

 75 by 40m in dimensions and provided with a thin, very Ught brown shell hav- 



