430 



GEOLOGICAL SURVEY OF THE TEREITORIES. 



Mandibulary palptis is four-jointed, bearing seven ciliate bristles, the 

 two basal and the three terminal ones being nearly straight (more so the 

 former) ; the two middle bristles have a stout base, 

 and are curved inwardly (Fig. 55 c). 

 cA.-— -\-\\ II I The first (anterior) (Fig. 57) and second antennae 



haTe their basal half, in very young forms, at least, 

 peculiarly ciliate. This is mentioned also by F. Span- 

 genberg, but not figured.- 



Second antennce. — At tbe 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 cilise 

 S^L\ ortiSter ^^^^^^^ (not in groups), and from the under side at its base 

 a siAg:io claw): Lower part the future first claspcr-hook begins to bud, which 

 ous ba°oTiiu8^"7l, eiTtcri^K then becomcs corrugate at its tip. An exuberant 

 thefurca. riasmaticmat- ^ell — complcx iu the basal piccc, formatiou of trans- 



ter and remainder of yolk | -jt i ^, ' ,,... „,, 



retreated throufih the ef- verse and lougitudmal musclcs, subdivision of the 

 feet of osmic acid. 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- ^_^-^^^^5:^::p^^=^=^=^'~-^2 

 mains but with ^-s^^^ /'^^ 

 muscular differ- 

 entiation; and at 



its inner base on ^^S- ^^- — S^*^ °^ ^'^^^ maslUa of Streptooeplialua texanus. 



a broad frontal protuberance, a number of hyaline cilise 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. 



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 ; plasmatic 

 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. 



LarvsB 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- 

 FiG.6o.-KigM male clasper PO^t for the embryonic>rca and is uot a musclc, 

 Eubranchipus, from life. A, but a chitiuous stick or Dacillus, which, after one 

 l;?ntitarite^;na;ji:lonk£xd\'ormore moults (Fig. 63) is pushed out, and its 

 nai^ muscles; E, first hook cor- intcgument bccomes ciliatcd. But the latter, after 

 rifuture inner angie'^wherefrom more moults, docs not bccomc the permanent 

 the terminus will twist. furcct^ as wc shouM cxpcct, for it is cast off with 



the other integument, and the typical development of the/wrca begins 

 (Fig. 62). 



