1883.] Heterogenetic Development in Diaptomus. 387 
Entomostraca, the significance of these facts cannot fail to appear. 
A similar parasite of Cyclops is Filaria medinensis} 
The Cladocera are generally quite free from parasites, but I 
have found in several instances young nematoids in the blood 
sinus in front of the heart in Daphnia magna.: These are mouth- 
less but very active round worms, subsisting upon the nutriment 
in the blood which constantly bathes the animal. True cysts 
could not be formed in the cobweb-like tissues of the hosts. 
This is, so far as I can learn, the first publication of Entozoa 
from Cladocera. The animals were from “Schimels Teich, 
Leipzig. While collecting Copepods near Tuscaloosa, Ala., I 
gathered a number of specimens of Cyclops tenuicornis and nearly 
all were unusally pale and feeble. On examination they proved 
to be infested with a worm of the sub-order’Distomex. This 
sub-order includes many distressing parasites and forms which are 
adapted to be widely distributed by a long period of adolescence 
and the number of Stages passed through before maturity is at- 
tained. 
The larvæ live frequently in Mollusca, and in maturity the ani- 
mal inhabits the intestine of vertebrates. 
Upon €xamination the Cyclops individuals collected were nearly 
all found affected, some having as many as five parasites of vari- 
F sizes about the alimentary canal, in the common vascular 
“ity which corresponds to the entire arterial and venus system 
ed the more highly organized Calanidz. The Cercarian or tailed 
TS Was not found. Were the life-history known it would prob- 
Y appear that the larval stage is passed within some young 
mollusks, and that the adult infests some vertebrate, probably fish, 
A ~~ Would thus be perhaps transferred either in food or drink to 
Stem. 
on i Worthy of notice that the host was soon destroyed by the 
the i T TE post-imago or Coronatus form being absent; most of 
; val oes thus infested possessed abnormally persistent lar- 
“aracters in antenne, etc, 
om EXPLANATION OF PLATE V. 
i pa r Diaptomus castor (? 
te ?), fifth pair of legs of adult male. N 
: 3 same (older specimen) showing a greater retrogra 
Oy es metamorphosis of inner ramus. - : 
> : caudal stylets of adult. 
ee, ee 
ae rt Ueber d. Bau. u. d, Entwicklung d. Faria medinensts, Moscow. 
