430 GEOLOGICAL SURVEY OF THE TERRITORIES. 
Mandibulary palpus is four-jointed, bearing seven ciliate bristles, the 
two basal and the three terminal ones being nearly straight (more so the 
former); the two middie bristles have a stout base, — 
and are curved inwardly (Fig. 55 ¢). 
ch---\ The first (anterior) (Fig. 57) and second antenne 
have their basal half, in very young forms, at least, 
/ peculiarly ciliate. This is mentioned also by F. Span- 
genberg, but not figured. 
Second antenne.—At the time of sexual differentia- 
tion the greater part of the bristles and the inner 
Fig. 58.—a. Same larva branch drop, the basal piece sprouts a few single cilize 
ei tet or ihe etiee with (NOt in groups), and from the under side at its base 
asingle claw) : Lowerpart the future first clasper-hook begins to bud, which 
of abdomen with a chitin- c 5 
ous bacillus, ch., entering then becomes corrugate at its tip. An exuberant 
ae eee Elser a cell—complex in the basal piece, formation of trans- 
retreated through the ef- verse and longitudinal muscles, subdivision of the 
fect of osc terminal piece of the antenna near its base, and bud- 
ding of a small roundish protuberance at the inner side of the middle 
piece takes place, and the male clasper is nearly developed. If a female 
specimen, the en- 
tire antenna re- eee 
mains but with Fas on he eee 
muscular differ- 
entiation; and at 
its inner b ase, on Fig. 59.—Seta of first maxilla of Streptocephalus texanus. 
a broad frontal protuberance, a number of hyaline ciliz appear. Some- 
what later the form of the female clasper slightly changes into one 
peculiar to this genus (Fig. 61), which is very vari- 
able in form. 
jy, At the time when in the male clasper the first 
/ hook is budding, the frontal tentacles are already 
present, but owing to their tendency to coil ven- 
trally and their small size I did not succeed in 
closely following their mode of origin (Fig. 60 B). 
In its early stage the margin is entire, with a con- 
tinuous row of large marginal cells; plasmatie 
contents in general intermingled with oil globu- 
les, and longitudinal muscles transversely striate. 
I think at a later time the latter will branch lat- 
erally, since the developed tentacle shows also 
transverse muscles. The peculiar mammiform 
excrescences along the margin are attained after 
several moults. . r 
Larvee with three branchipeds budded, the first 
of which, with a single claw, show the develop- 
ment of the post-abdominal furca, as illustrated 
by Fig. 58. I am of the opinion that the narrow 
piece running along the end of the body is a sup- 
Fic. 60.—Right male clasper POTt for the embryonic fwrea, and is not a musele, 
Eubranchipus, from life. A, but a chitinous stick or bacillus, which, after one 
Pant, dd antennas D lonsitnds OF more moults (Fig. 63) is pushed out, and its 
eae ae Brea integument becomes ciliated. But the latter, after 
¥, future inner angle wherefrom More moults, does not become the permanent 
Wino Homerton Wall ines Jurca, as we should expect, for it is cast off with 
_ the other integument, and the typical development of the furca begins 
(Fig. 62). 
