1884.] Zoology. 429 
ZOOLOGY 
TREMATODE PARASITES IN AMERICAN CRrayFisH.— Professor 
Kellicott has recently called attention to the fact that American 
St he e subject to invasion by Trematode parasites.! His 
iy yi ats recalled to me some observations which I made in 
iA = ži E I now record, because in the interval the Dis- 
feteueg e tropean Astacus fluviatilis have been subjected to 
ge examination, and one of them has been accused as the 
eof the pest, which has, within the last five years, effected 
Two Distomes are found abundantly in Astacus—D. isostomum 
The 
BET. 
PeT i 
ra measures between 2 and 3™™ in 
i. ome is ey recognized by 
ity in diameter of it i 
ventral suckers s anterior an 
less to its h i 
, ost, 
that ca a and Zaddach thinks 
See 
rds my impression that I have also met 
: Sostomum in American crayfish, 
but th 
“are ‘ Ge have preserved 
i ; Fic. 1.—M, the mouth in 
The minute eac out Self impregnating. ‘he anterior sucker: m Ihe 
E Professor een led forms described by front of vs, the epin ox 
2 young stages tt, are very probably er; ic, one of the intestinal 
my of this species, _ coeca ; vd, vas deferens lead- 
One which ection of Trematoda I find '% directly from the anterior 
I mar d 
testis ? to cs; vé, the vitel- 
Z ked, when discovered, “D. logen; ż,the posterior testis, 
3 S from a cyst in the ovary the vas deferens of which 
This “us, probably appears to end in a vesicula 
> Species (Fis y ©. Propinquus. seminalis, between whic 
fh 1g. 1), belongs to a small andzd is the blastema for 
1 Proe. mes in which the anterior the ovary. 
: 2C.0. ay, mran, Chicago Meeting, 1883, p. 115. 
ae Bericht eae ee Krebspest, &c.” Wien, 1881. Rev. by Dr. v. 
Thiere in Archiv. für Naturg., 1883. 
1 Zodl. Anz., 1881, 398 and 426. 
