I'M S'OGOXIDA 



now .1 ; mbryonal legs and sometimes the chelifori hi 



:i, tin byssus-gland reduced, and the byssus-threads disappeared, 

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

 a young one obtains its complete shape, and now onlj grows in size and 

 men) of thorns and bristles; not till now appear the genital pores, or 

 , and t h e gland-p 

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

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

 m 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 01 law. Where one or both pairs are 

 wanting in the growu animal, probabl) neither of them appear at all. 



I have drawn the third larval stage ■•! Nymphon grossipes^ pi. I, Eig. 26- 29, A', robustum, pi. II, 

 ■w. pi. II, fig. 14, and Pseudopallene circularise pi. I, Kg. 15. Besides the general remarks 

 stated above, I must especiall) point out that the palps immediately at their appearance 

 fen n d in quite another place than the first pair of embryonal legs just disappear! 

 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. 2j </ and b with tit;. 2 \ 6 and c. - Furthermore the palps in the first species 

 -urc 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. circularise 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 

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

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



he small, but powerful, well developed embryonal legs. In the drawing of Pseudop. circula 

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

 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, 



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



a, how the same pairs oi ses and appendages have changed, the processes having become 



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



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



-p., finally, in which the fourth paii ol ambulator) legs are very long, and which is of an 



iwing I have given of V. grossipes^ pi. I, Kg 26, the beginnings have 

 rther than to form a pair of semiglobular tubercles before the base oi the Krst pai oi 

 ami. 



mentioned, Dohrn, Bau u. Entwickl. Arthrop. 1870, pi. VI, Kg. 11 13, lias given 



