426 GEOLOGICAL SURVEY OF THE TEERITOEIES. 



again. T did not observe tliis, but found that older larvre keep con- 

 stantly creeping over the mud, and do not so actively swim about as 

 other Branchipodidce do. 



I received about a pound and a half of dried clay-mud of a greyish, 

 color from Kansas, of which from five to ten grammes were used at the 

 time for each experiment. 



Plate XXXV (except figs. 3 and 4 a) refers to Ap^is lucasafius, of which 

 I obtained but three advanced stages. A very high and uniform tem- 

 perature appears to be necessary to keep them alive. 



Estheria compleximanus (Plate XXXV, figs. 3 and 4 ft) was frequently 

 hatched, even at a temperature of 45° to 50° F., but 1 have unfortu- 

 nately neglected to follow up its stages of development. It is a limni- 

 colous, ostracod-like crustacean. The older larvae, as well as the adult, 

 like to dig and make furrows in the clay. I have seen them also swim- 

 ming in coptila for several seconds. The JSfauplius is extremely minute, 

 and has on either side two long, broad, juxtaposed spines (one a little 

 higher up than the other) at the posterior side of its carapace. In the 

 adult the shell- duplicature is of an elliptic form and of milk-white color. 

 It is frequently cast off, but no notes were taken as to the number or 

 manner of castings. They seem to take up their food while making fur- 

 rows in the clay ; the carapace protects the branchipeds which x>addle 

 continuously while the animal feeds. 



With every moult a new addition of limbs is effected, an advanced 

 specialized structure attained, until after the sixth or seventh moult of 

 Streptocephalus, when of about 3™"^ in length, the inner genital glands 

 make their appearance, followed by the outer, and shortly afterwards a 

 change of the second pair of antennae is noticed, simultaneously with, 

 the full development of the eleven pair of feet. To avoid repetitions as 

 to the gradual development of the latter, as well as of the inner and 

 outer genital organs and the furca, I must refer to C. Claus and F. Span- 

 genberg's papers. 



I presume that the chorion proper in all Branchiopodidae, situated 

 between the exochorion or outer shell and the amnion or inner egg- 

 membrane, has the same structure as that of Arpuhis and is similarly 

 acted upon by water (under conditions peculiar to each sijecies), de- 

 scribed and figured by C. Claus. 



The egg of Streptocephalus texamis is rather small, when dry, x>artly 

 transparent, brownish, and measures three-tenths of a millimeter in 

 diameter. It is of spherical shape and finely granulated. 



The egg of Apiis lucasanus is larger, brown, and measures one-half 

 millimeter. Its exochorion is of the same structure as that of Apus 

 cancriformis, showing large, thick walled polygonal markings. 



The Xauplius-stage of Streptocephalus texanus does not in the least 

 differ from that of Branchipus stagnalis of Europe, perhaps the whitish, 

 instead of yellow color excepting. The first acinaciform or saber-shaped 

 hook-bristle is on the inner side of the first or basal segment of the 

 second antennae. It is naked and becomes beset with two rows of fine 

 ciliae after the first moult, and after another moult it is split into two 

 unequal flat termini, which are also ciliated. The second segment also 

 bears a long flat and bent-inward hook-bristle, which is first naked and 

 ciliate alter the first moult. The second antenna terminates likewise 

 with two branches, the shorter inner one bearing three long bristles, 

 the outer longer having five long bristles arising from four segments. 

 The second antennae are the principal parts of locomotion, and give the 

 larvae the appearance -of little white pigeons. The second antennae re- 

 main in their previously described shape until a time when sexual dif- 

 ferentiation takes iDlace. 



