Entozoa of British Marine Fithea. 7 



'2!) mm. ; brea<ltli \ of the K'nj^tli ; neck also ^ of the length, 

 niitl tho posterior horder of the bocoikI testis about the same 

 distatico from the posterior end of the body. Pharynx 

 •09 nun.; CBsopha;^ns "105 mm.; excretory vesicle extendin;^ 

 forward to anterior end of ovary. Ovary ch)3e in front of 

 testes, trilobate. Reccptaculum seniiniH immediately in 

 front of ovary. Testes directly tandem or very sli^^htlv 

 oblique, round, isodiametric ; diameter •20 mm. ; separated 

 by yolk-gland.'«. Yolk-glands extendiiifr forward to posterior 

 border of ventral sucker ; not discontinuous at testes. Vesi- 

 cula sennnalis extending 'l--!? mm. behind ventral sucker, 

 I. e. about 1^5 of length of body, or rather more than half tho 

 diameter of the ventral sucker. 



From the above notes there can be little doubt that the 

 specimens under con^iideration are actually Podocotyle atomon. 

 A fact which might cause jiesitation in admitting this identi- 

 fication is that Odhner his frequently found a closely allied 

 species, P. reflexa (Crepl.) in Gastrcta sjn'ttachia (Spinackia 

 vulgaris). According to Odhner, this species differs from 

 P. atomon in being much more elongated, less flattened, and 

 in having the suckers more nearly approximated. Other 

 features noted by Odhner are the great [)rominence of the 

 ventral suckers, the length of the oesoj^hagus relative to the 

 pharynx, the greater breadth of the testes, the greater length 

 of the cirrus-pouch, the median position of the ovary, and 

 the discontinuous condition of the yolk-glands. The majority 

 of these characters, however, are of little value when dealing 

 with such a species as Podocotyle atomon. It does not require 

 a very extensive study to convince one that Podocotyle atomon 

 is within certain limits a very variable species, and it is just 

 in the above-detailed features that the variation occurs. No 

 weight can be placed on the length of the oesophagus, for in 

 Podocotyle atomon it may be shorter than the pharynx, or, as 

 Miss Lobour notes, more than double its length, de|)ending 

 almost entirely on the state of contraction of the body. 

 Again, the testes not infrequently exceed half the breadth 

 of the body, and the ovary may be only very slightly, if at 

 all, displaced from tho middle line. The yolk-glands are 

 extrtmely variable and may be entirely absent between 

 the testes or may lill u|) a considerable part of the inter- 

 testicular space ; further, they are lairly often discon- 

 tinuous laterally at the level of the intertesticular space 

 or the posterior testis. The cirrus-pouch may extend barely 

 beyond the ventral sucker, or it may occasionally reacii 

 nearly halfway to the ovary. The extended condition of 

 the body and the prominent pedunculated appearance of 



