PYCNOGONIDA. 



gerous legs, now appear, after the embryonal legs and sometimes the chelifori have 

 been thrown off, the byssus-gland reduced, and the byssus-threads disappeared. 

 Moultings also take place during the development of this larval stage, until the 

 animal as a young one obtains its complete shape, and now only grows in size and 

 outer investment of thorns and bristles; not till now appear the genital pores, or 

 openings, and the gland-pores. 



The point of the development of this stage which is of most interest, is the rise and growth 

 or development of the imaginal fore limbs. Of the two pairs of limbs the foremost one, the palps, 

 seem to develop a little earlier and somewhat faster than the hindmost one, the ovigerous legs, but 

 I have too few examinations to venture to regard it as a rule or law. Where one or both pairs are 

 wanting in the grown animal, probably neither of them appear at all. 



I have drawn the third larval stage of Nymphon grossipcs, pi. I, fig. 26 29, N. robitsfiu/i, pi. II, 

 fig. 7, N. spinosum, pi. II, fig. 14, and Pscudopallene ctrcutaris, pi. I, fig. 15. Besides the general remarks 

 stated above, I must especially point out that the palps immediately at their appearance are 

 foxind in quite another place than the first pair of embryonal legs just disappeared, 

 that is to say, quite anteriorly behind the base of the proboscis, at a considerable distance from the 

 ovigerous legs, while both pairs of embryonal legs from their rise to their being thrown off are almost 

 in contact at their base, arising together from the hindmost part of the lower surface of the first 

 chief division, cp. fig. 27 a and b with fig. 24 b and c. - Furthermore the palps in the first species 

 are sure enough proportionally considerably longer than the ovigerous legs, but in the palps the seg- 

 mentation is at most only indicated, a fact intimating that no moulting has taken place after the 

 beginning of the limbs, and that these latter have only arisen during this phase of the third stage. 

 In the fourth species, Pseudop. circular is, of course only the ovigerous legs have arisen, but their 

 development has not gone farther than to their being segmented inside the smooth epidermis, and 

 thus they have not reached the second phase. The small particular drawings that in pi. I, fig. 28 and 

 29 have been given of the first beginning of the palps and ovigerous legs, show the common type 

 of the beginning of legs in Arthropoda, and I think it impossible to interpret them as the reduction 

 of the small, but powerful, well developed embryonal legs. In the drawing of Pscudoj). circularis I 

 have given the greater part of the ganglionic system with the four large ganglia of the body, the 

 very small abdominal ganglion, and the large, foremost ganglion, i. e. the coalesced ganglia correspond- 

 ing to the embryonal legs, or the nethermost pharyngeal ganglion, ganglion suboesophageum. By 

 comparison with the same nethermost pharyngeal ganglion in the second larval stage, fig. 12, it is 

 seen, how the same pairs of processes and appendages have changed, the processes having become 

 rather smaller, while the appendages have become large, lengthened, tapering to a pair of nerve 

 threads which I have been able to follow some way in the direction of the ovigerous legs. In Pall, 

 acus n. sp., finally, in which the fourth pair of ambulatory legs are very long, and which is of an 

 appearance almost like the drawing I have given of N. grossipes, pi. I, fig. 26, the beginnings have 

 not gone farther than to form a pair of semiglobular tubercles before the base of the first pair of 

 ambulatory legs. 



As already mentioned, Dolirn, Ban u. Entwickl. Arthrop. 1870, pi. VI, fig. n 13, has given 



