26 PYCNOGONIDA. 
going, also a couple of larvæ on the second stage, but not of the same degree of development. In 
the younger of these larvæ, pl. II, fig. 11, the three foremost pairs of ambulatory legs are all developed, 
and, contrary to what commonly is the case, all developed to the same degree. The byssus-gland is 
also earlier developed than usual. In the somewhat older larva, fig. 12, the first pair of ambulatory 
legs are, as usual, much more developed than the second pair, and the third pair is not even 
to be seen. 
Of Nymphon Sluiteri I have also drawn a phase of the second stage, pl. II, fig. 17, viewed from 
the side, and fig. 18, viewed from below, but they show nothing remarkable with regard to the develop- 
ment of the limbs. 
Of Pycnogonum littorale I have an interesting drawing, pl. I, fig.4. The specimen was taken 
a score of years ago by the present doctores, Mr. Hector Jungersen and Mr. Johannes 
Petersen, at Frederikshavn without particular statements as to the circumstances im which it was 
found. It can be no other than a larva in the close of the second stage of a Pycnogonum s.str., but 
from Frederikshavn and upon the whole from Denmark we know of no other -ycnogonum than P. 
littorale, which moreover is commonly found on the locality in question. The embryonal limbs have 
already quite disappeared, and 10 traces are to be seen, either from the upper side, represented here, 
or from the lower side. That these limbs have disappeared is no wonder, as they usually do so, if 
not so quickly, at all events in a short time; more remarkable is the absence of the chelifori. Im 
other instances the chelifori are embryonal limbs which are kept throughout the life of the animal, if 
not always with a fully developed chela, at all events, though, with fragments of it, and only im a 
few forms, the genera Pycnogonum and Phoxichilus, the so-called order «Acerata» of Sars, and in 
his family Co/ossendeidæ, the chelifori are quite wanting in the full-grown animal; there is, however, 
a great possibility that the chelifori of the last-mentioned family are not thrown off until an advanced 
stage, after the close of the larval development. Such, at all events, is the case in Co/ossenders 
angusta (and gracilis) according to the observations of Hoek, which observations I shall here aug- 
ment very much (in another Co/oss. (macerrima) I have found the chelifori thrown off already in a 
very young animal). The larva of Pycnogonum drawn here, is, judging by the development of the 
ambulatory legs, in the close of the second stage, all three pairs of legs having reached the full seg- 
mentation, also the claw. The body and the legs are smooth and naked, without the thick, rugged 
exoskeleton distinguishing the grown F-ycnogonum, and only the oculiferous tubercle and the three 
knobs in the middle line of the back remind: of the rugged appearance of the animal. The first seg- 
ment of the trunk is uncommonly and unproportionally large. 
The genera Pa//ene and Pseudopallene are distinguished from the other Pycnogonida, not only 
by the above mentioned absence, or rudimentary state of the embryonal legs, but also by the two 
foremost pairs of ambulatory legs arising contemporaneously, growing, and attaining to a considerable 
development, before the growth of the third pair of legs begins. Of Pa/l/ene I have examined two 
species, Pa/lZl. brevirostris and Pall. hastata. "The former, Fall. brevwrostris, is given on a rather early 
stage, in which the two pairs of ambulatory legs are somewhat short and thick, with a single con- 
striction in the middle besides the claw, pl. I, fig. 16; a special distinetion is the separation, already 
mentioned in the foregoing, of the byssus-gland in particular dermal glands, each with a byssus-thread 
