TAPEWORM PARASITIC IN THE STICKLEBACK. 135 
it would result in the easier capture of the Cyclops by the stickle- 
back, and thus ensure the larva a better chance of attaining 
maturity. 
The Cyclops is swallowed by the stickleback, and in the intestine 
of the latter the larva is set free to grow into the normal adult. 
SUMMARY. - 
1. The paper contains a description of a tapeworm parasitic in 
Gasterosteus aculeatus Artedi. I regard this tapeworm as Jchthyo- 
tenia filicollis Rud., though the absence of an adequate 
description of the species and the confusion into which the 
nomenclature has fallen, make the identification a matter of 
considerable difficulty. The synonym, Proteocephalus Wein., 
used by La Rue (12), does not seem to me justifiable. 
2. An account is given of the anatomy and histology of the 
species. With the exception of one or two details, this account 
agrees closely with that given by Benedict (3) and by Kraemer (10). 
3. Though many conjectures have been made with regard to 
the life-history of /. filicollis, no reliable information has hitherto 
been published. The evidence given in this paper shows that 
Cyclops varius Lillj.is the intermediate host. This conclusion 
is based upon successful experiments to infect the Cyclops hy the 
tapeworm egg, and to infect the stickleback by the larva In the 
Cyclops. Direct infection of the stickleback proved impossible. 
4. A short account is given of the segmentation of the egg 
and the development of the larva. Though incomplete in some 
respects, it was found that it followed the general course described 
by van Beneden (2). 
LITERATURE. 
(1) Bertincuam.—Annals of Nat. Hist. vol. xiv., 1844. 
(2) Benepen, E. van.—‘‘ Recherches sur le développement 
embryonnaire de quelques Ténias.” Arch. de Biol. 
vol. ii. 1881; Journ. R. Micr. Soe. vol. 1. 
(3) Benepicr, H. M.—* On the Structure of Two Fish Tape- 
worms from the genus Proteocephalus Weinland, 1858.” 
Journ. Morph. 1900, vol. xvi. No. 2. 
(4) Buarnvitie.—Dict. des Sci. Nat., t. Ivii. p. 552. 
(5) Braun, M.—Vermes. Abt. 1 6. Cestodes, in Drs H. G. 
Bronn’s “Klassen und Ordnungen des Tierreichs.” 
Leipzig, 1900. 
(6) Copsotp.—Transact. Linn. Soc. xxu., 1856. 
(7) Drestne, C. M.—‘‘ Systema Helminthum.” Vienna, 18950, 
vol. 1. 
(8) Dusarpiy, F.—‘ Histoire Naturelle des Helminths ou Vers 
Intestinaux.” Paris, 1845, 
