428 



GEOLOGICAL SURVEY OF THE TERRITORIES. 



underlying cells, in fact tliey are prolongations of the latter. This 

 change takes place in our Streptocephalus at a time when the eleventh 

 pair of branchipeds has made its appearance and 

 the stalked eyes which laterally bud out of the head 

 are already contracted behind and jprovided with 



'Fig. 51.— Streptocephalus Fig. 52. — Eiglit clasper c? Streptocephalus texanus Pack. oc. eye. 

 texnuus — rijibt clasper cT 

 larva 4""» in length. 



a stalk, while in BrancJtipiis stagnalis the change in the second antennae 

 takes place earlier. 



The three protuberances do not appear before the accumulated cell- 

 masses have pushed out on the iDuer side of the antenufe in a down- 

 ward direction part of the main branch of the male forked clasper. At 

 the time when the latter just begins to fork at its tip a second inner 

 brauch is budding near its inner base (Fig. 51). 



The reuiainder of the former second antennoe grows out into the outer 

 long flat branch of the clasper, but, as in the aquarium the full grown 

 form is seldom reached, I could not (jlosely follow the development of 

 this outer branch in detail. The new clasper shows in its entire length 

 polygonal cells in the integument, which, after another moult, Imve 

 partly disappeared, being then permanently confined to but a few spots 

 on the inner rounded corrugate sides of the same. 



rig. 53. — 2 streptocephalus tex- 

 anus, right clasper. 



Fig. 54. — Cast-off skin of suhima<ro-stage Strepto- 

 cephalus texanus left male clasper from above. 



III.— Larval stages of Eubranchipus vernalis Yerrill. 



During the whole summer of 1880 I experimented with dry mud from 

 ponds inhabited by either the normal or pale race of this Branchiopod, 

 but all in vain. "Neither jars kept on ice in a large refrigerator, nor 

 frozen, dampened mud, gradually or suddenly thawed, developed any 

 larvte. The mycelium of a fungus, a few Daphnidiie, and microscopic 

 organisms were the usual result. 



However, I obtained a few early stages of the pale race and many 

 specimens of the later stages of the normal form from the ponds them- 

 selves. The latter are reddish and already pigmented when but 4"^'" in 

 length, while those of the pale race were dull white. 



Eubranchipus larvae are comparatively much stouter and larger in 

 their first stages than their allies. Larvae of 0.8™'" in length with the 

 first three branchipeds budded out and (osmic acid prep.) nine more 



