386 Heterogenetic Development in Diaptomus. 
(Apri, 
but both rami are 3-jointed as in the swimming legs of other 
Calanide. On the other hand, regarding both legs as present, the — 
“hand” of the male does not homologize with the left limb, and 
we have besides to account for a supernumerary 2-jointed limb on 
the second joint of the abdomen.. 
The present species was found in large numbers in Mulbeny 
creek, Cullman county, Alabama; the color is bluish-green, and 
the length about ,f in. | 
ENTOZOIC PARASITES IN ENTOMOSTRACA (Fig. 15, Pl. vi). 
We have discussed the relation of the minute fresh-water Crus- 
tacea to sanitary science in a paragraph in a recent article in the 
NATURALIST, but it remains to touch upon another phase of the - 
subject. It may be thought unnecessary to trouble ourselves 
about the pathological conditions prevailing among such lowly 
animals, but it can be shown that these same causes of disease 
may not be unimportant in connection with human diseases. 
It is a fact constantly receiving new exemplification, that the 
parasites infesting small animals, particularly water animals, aid. 
frequently but the immature forms of parasites of animals higher 
in the scales. These alterating generations are exceedingly 
cult to study, so that while all stages may be separately 
only a fortunate combination of circumstances or patient accum 
lation of facts can connect the individual factors into the complet | 
cyclus. 
Thus, for example, Professor Leuckart has but recently worked | 
out the full life-history of Diéstomum hepaticum, although ~ 
adult has been a stock example in helminthological study i 
laboratory for years. ome 
_ The importance of such parasites, even in a commercial a : 
needs but a reference to trichinosis to illustrate. I am not pe 
that endo-parasites are known in Entomostraca except in er 
of Cyclops. Embryos of Cucullanus elegans, a nematoid ee 
enter the body-cavity of Cyclops and undergo two molts ar 
are transferred to the intestinal canal of food-fishes:" | 5g 
Taken in connection with the recent discoveries n p : 
Forbes, showing how dependent our own food-fishes €? $ 
1Claus. Kleines Lehrbuch d. Zoologie, p. 368. pALisT> jem 
3 Forbes. On some Entomostraca of Lake Michigan, AM. NATU. a : 
1882. . 
Cf. Ryder on Food Fishes, Bul. U. S. Fish. Com. 
