1883.] Heterogenetic Development in Diaptomus. 499 
HETEROGENETIC DEVELOPMENT IN DIAPTOMUS. 
BY C. L. HERRICK. 
( Continued from page 389.) 
CycLops INGENS Herrick (Cyc/ofide of Minn., p. 228, Plate 1v, Figs. 1-8). 
Found in pools near Tuscaloosa, Ala., with ee pulex and Simocephalus 
daphnoides, The post-imago is somewhat over 4} in. long, ż. e., not quite as long as 
C. gigas according to Brady, which is very little cee Our form has longer sty- 
lets and shorter antennæ in the ordinary stage, but the mature or post-imago has 
shorter stylets. In the last stage prior to maturity the stylets are just as figured by 
for this stage. It is worthy of remark that C. 4aufmanni Uljanin, which is 
certainly founded upon a prematurely gravid larva (feet ities eee and antennz 
: undifferentiated) corresponds perfectly with larvee of C. ingen 
Brady himself considers C. keleri the same species, and we 
| have here apparently an older stage with fully developed feet but 
not yet provided with mature antennz. 
A variety of C. ingens is found in cold springs at Tuscaloosa 
and elsewhere in Alabama, much less in size and with the propor- 
__ tions of the European C. gigas. 
__ The large examples in shallow “prairie pools” were masked 
“P P 
by dense alge coating. The form of the fifth foot and stylets dis- 
tinguishes the above from other members of the genus, and one 
> tempted to regard these forms as varieties of C. gigas simply. 
Parcus (Cyclop. Minn., p. 229) might be considered avar. of C. 
- PECTINATUS, sp. nov. (Plate vi, Figs. 25-28). 
t aat to C, navus, from which it is chiefly distinguished by a semicircular series 
the spines af the iest the greatly elongated caudal stylets. In the post-imago 
beet e nearly a as long as the abdomen ; the antennæ reach p to the 
4 a Most characteristic, ngaei is a circlet of small spines one- 
ston base of the stylets. Length o in, 
R es sp. nov. (Figs. 24-25, Plate v; — 20-21, Plate vi). 
Section with r7-jointed antenn 
elongated; antennz reaching a little bul the first thoracic segment, 
short, iai ia, ed formula =% o -©£ o_ vuevuuy yvy , the terminal joint rather 
joints e.g. te three teeth near the extremity; antennules rather long, last two 
oo nen a fifth foot 2-jointed, second joint with two nearly equal set; cauda 
ae 7 tenuic enuicornis , of spermathzeca elongated. 
Tyk iS species is the most slender Cyclops known to me, and 
be recognized by the toothed terminal joint of the antennæ, 
e crie confined to C, tenuicornis, “ coronatus stage.” 
35 
