ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
373 
Ectoparasitic Trematoda.* * * § — Herr 0. Diechhoff commenced Lis in- 
vestigations on the ectoparasitic Trematodes with a view of solving the 
question raised by Ijima as to the existence of a connection between the 
female generative apparatus and the digestive tract in ectoparasitic 
trematodes ; but it has extended itself to an investigation into the 
anatomy of Octobothrium lanceolatum, 0. Merlangi, and Polystomum 
ocellatum. 
The author finds that in Polystomum integerrimum the vitello- 
intestinal canal is a structure which it is difficult to overlook; the wall 
consists of connective tissue invested by epithelium with a moderately 
large number of nuclei ; the canal is found either empty or filled with 
sperm or yolk substance. Its connection with the enteric wall is very 
peculiar for it runs for some distance beside it, and then enters at an 
angle in such a way as to form a cup-shaped projection. By this 
arrangement the compression of the intestine prevents the entrance of 
the enteric contents into the genital ducts. The arrangements of the 
canalis vitello-intestinalis in P. ocellatum, Octobothrium Merlangi, O. lan- 
ceolatum, Diplozoon paradoxum, Axine belonis are next described, and the 
existence of this connection between the enteron and genital duct safely 
established. 
Detailed accounts are then given of the anatomy of the already- 
mentioned Trematodes. 
Vitelline nuclei of Distomum Richiardii-t — Dr. C. Crety finds 
vitelline nuclei in variable number in the ova of this Trematode. He 
criticizes the various opinions held in regard to similar bodies in the ova 
of other animals, and believes that in D. Richiardii they are formed 
endogenously within and afterwards fuse with the protoplasm of the 
ovum which stains like chromatin. No other Helminth is known to 
have vitelline nuclei in its ovum, but in D. megastomum and Hexacotyle 
Tynni there are analogous ditfuse granules. 
Suckers of Distomum.j — Dr. C. Crety describes the structure of the 
suckers in Distomum megastomum and D. Richiardii, and finds abundant 
ganglionic cells, from the presence of which he infers the tactile func- 
tion of these organs. 
Anatomy and Histology of Cestodes of Freshwater Fisher.§ — 
Herr A. Kraemer finds that the Taenim of Fish as distinguished from 
those of warm-blooded Vertebrates present the following characters ; the 
absence of a rostellum, in place of which there is often a fifth, small, 
sucker occupying the front end of the scolex ; the presence of this apical 
sucker is certainly a primitive character, peculiar to the lower form of 
Taeniae. The strobila are relatively short, their joints are closely con- 
nected with one another ; no terminal joints are cast off ; at the tip of 
the last, and, as a rule, conical joint of the chain there opens the 
terminal vesicle of the excretory system, into which all the longitudinal 
vessels open. The excretory apparatus opens by means of fine canali- 
culi in the neck and the youngest joints ; these branch off from a capil- 
* Arch. f. Naturg., Ivii. (1891) pp. 245-76 (1 pi.), 
t Atti R. Accad. Lined (Rend.), ser. v. vol, i. (1892) pp. 92-7. 
j Tom. cit., pp. 21-6 (2 figs.). 
§ Zeitschr. f. Wiss. Zoul., liii. (1892) pp. 647-722 (2 pis.). 
