331] PSEUDOPHYLLIDEA FROM FISHES— COOPER 43 



seems to be due to the proximity of the highly specialized proboscides to which 

 it sends large branches. The excretory system is likewise built on the typical 

 plan, the posterior connections with the exterior being, in fact, quite like those 

 of B. SCOT pa. On the other hand, the terminations of the nervous and excretory 

 systems in the secondary strobila, both anteriorly and posteriorly support the 

 view that the latter is not homologous with the strobila of other bothriocepha- 

 lids. What was formerly described as the ring commissure must now be con- 

 sidered as merely a secondary formation due to the fusion of the severed ends 

 of the chief strands; which statement is also applicable to the terminal vesicle 

 of the excretory system. And this, in spite of the fact that the secondary scolex 

 is quite similar to the true scolex of other forms in that it is supplied with two 

 sets of muscles which are not found in the foremost segments, but are peculiar 

 to the scolex. 



Since there is considerable evidence in the literature on cestodes to show 

 that the prominent posterior borders of the foremost segments of many species 

 are developed as accessory organs of attachment or for locomotion (cf. Spengel, 

 1905:281), the question might well be raised whether external segmentation 

 in Haplobothrium is palingenetic or cenogenetic in its nature, particularly 

 since it is confined to the anterior region of the secondary strobila. The facts 

 that no such appendages are present in the primary strobila and that the 

 posterior end of the secondary one is not segmented, apart from the consecutive 

 sets of genitalia, would seem to point to the original condition being one in 

 which external segmentation was absent as in Ligula or Triaenophorus. Since, 

 however, in the middle region of the secondary strobila there is an actual 

 correspondence between the external and the internal segments, it is quite 

 probable that the external segmentation is much older than might at first 

 appear, while the ligulate condition of the posterior end may have developed 

 secondarily. It is well to remember, too, in this connection that according to 

 Liihe (1898:285) Ligula has descended from fully segmented bothriocephalids. 



The subfamily, which up to the present contains only one genus and one 

 species, bears a general resemblance to the Diphyllobothriinae. It differs 

 from the latter, however, in that the genital organs are simple in each proglottis; 

 the vitelhne follicles are medullary; the testes are within (i.e., medial to) the 

 nerve trunks; the seminal vesicle is not strongly muscular; the cirrus is armed 

 with minute spines; the receptaculum seminis is medium sized; while the uterus 

 is divided into a uterine duct and uterus-sac as in the Ptychobothriidae. 



HAPLOBOTHRIUM Cooper 1914, e. p. 

 Haplobothrium Cooper 1914:1-2, 1914a:115 



Borders of the terminal disc of the secondary scolex and of the posterior 

 auricular appendages of both scolex and anterior segments provided with min- 

 ute spines which disappear with the appendages farther back. Nervous system 

 consists of two chief strands situated in the medullary parenchyma outside of 

 the vitelline follicles, uniting in the anterior end of the secondary strobila to 

 form a secondary nerve ring, and eight collateral strands, four arranged around 



