426 GEOLOGICAL SURVEY OF THE TERRITORIES. 
again. JI did not observe this, but fonnd that older larvee keep con- 
stantly creeping over the mud, and do not so actively swim about as 
other Br anchipodide do. 
IT 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 XX XV (except figs. 3 and 4a) refers to Apus lucasanus, 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 XXXYV, figs. 3 and 4a) was frequently 
hatched, even at a temperature of 45° to 50° F., but I have unfortu- 
nately neglected to follow up its stages of development. It is a limni- 
colous, ostracod-like crustacean. The older larvee, as well as the adult, 
like to dig and make furrows in the clay. I have seen them also swim- 
ming in copula for several seconds. The Nauplius 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 paddle 
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 antenne is noticed, simultaneously with 
the full development of the eleven pair of feet. To avoid repetitions as 
to the graduai development of the latter, as well as of the inner and 
outer genital organs and the furea, I must refer to C. Claus and F. Span- 
genbere’s S papers. 
I presume that the chorion proper in all Branchiopodide, situated 
between the exochorion or outer shell and the amnion or inner egg- 
membrane, has the same structure as that of Argulus and is similarly 
acted upon by water (under conditions peculiar to each species), de- 
scribed and figured by C. Claus. 
The egg of “Streptocephalus texanus is rather small, when dry, partly 
transparent, brownish, and measures three-tenths of a millimeter in 
diameter. It is of spherical shape and finely granulated. 
The egg of Apus 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 Nauplius-stage of Streptocephalus texanus does not in the least 
differ from that of Branchipus stagnalis of Kurope, 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 antennsz. It is naked and becomes beset with two rows of fine 
cilie 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 after 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 antenne are the principal parts of locomotion, and give the 
larve the appearance of little white pigeons. The second antenne re- 
main in their previously described shape until a time when sexual dif 
ferentiation takes place. 
