170 ILLINOIS BIOLOGICAL MONOGRAPHS [458 



ing no operculum. The color is so faint that it can be seen to advantage only 

 when the eggs are in masses or in the uterus-sac. Ariola (1900:397) gave 

 the measurements of the eggs of the European species as 67 by 32ju. The larg- 

 est examined were immature, the contents consisting of large spherical cells 

 only, like those shown by Wagener (1854a) in his figure 6, Taf. I. When the 

 worms are stiU attached to the waU of the intestine of the host between the 

 mucous folds, they often discharge many of their eggs from most of the posterior 

 proglottides when their scoUces are irritated with a blunt needle in order 

 to make them loosen their comparatively firm hold. 



Forty-four specimens of Merluccius bilinearis were examined at Woods 

 Hole and at Harpswell, but no definite idea of a possible intermediate host was 

 obtained. It was noticed, however, that when the intestine of the fish con- 

 tained much grey chyle, presimiably the result of the digestion of small her- 

 ring — definitely ascertained at South Harpswell to be such in a few cases- 

 and of Pomolobus aestivalis (Mitchill), the blueback — no tape-worms of this 

 species were present; but where amphipoda were found in the stomach or the 

 remains of such in the intestine the worm was plentiful. Furthermore, where 

 nothing was found in either stomach or intestines, other than yellowish 

 chyle in the latter — as in most fish examined — indicating amphipods and 

 other small crustaceans as food rather than small herring, the worm was also 

 common. AU stages from the youngest strobilas, such as that shown in figure 

 49, to the oldest were found, but none nor any plerocercoids were met with in 

 the course of the thoro dissection of the available stomach contents of the 

 hosts, both fish and crustaceans. In a number of cases, nevertheless, only very 

 young strobilas were found in the intestine of the host, thus pointing to possible 

 sudden infections at different times. Wagener, who figured the youngest 

 strobila that has yet been recorded, in fact nothing much more than the scolex, 

 said nothing more concerning the fife history than that, on account of the ex- 

 cretory vessels opening separately to the exterior in this very young specimen, 

 there might possibly have been a vesicular appendage to the larva in the 

 nature of an enveloping cyst comparable to that described and figure for 

 "Dibothrium. (Belones?) " from Scyllium canicula, concerning which he said 

 (I.C., p. 45): "Vergleicht man diese Form vom Cysticercus mit den vorigen 

 [Cysticercus fascicolaris Rud.], so ergiebt sich, das der Unterschied nur in 

 dem Aufhangebeutel sich findet, der Kopf und Blase verbindet. " 



A detailed description of the species is here given, not only because it is 

 evidently the only one belonging to the genus, but because descriptive details 

 are so lacking from the European hterature that the determination of the spe- 

 cies is attended with considerable uncertainty. The writer, however, considers 

 that, on the basis of the pubhshed accounts and reports of the species, but 

 in the absence of European material for comparison, the form occurring on 

 this side of the Atlantic Ocean must be looked upon as identical with the C. 

 crassiceps of Europe. 



The material studied consisted of No. 204, 259, 261, 262, 269, and 282 in 

 the writer's collection from the intestine of Merluccius bilinearis as above listed. 



