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PYCNOGONIDA. 



as direct continuations of the embryonal legs. For my part I mnst regard it as a decided fact 

 that in all Pycnogonida the embryonal legs are quite thrown off during the second 

 larval stage, and that they are in no way identical with the later imaginal fore 

 limbs, the palps and the ovigerous legs, which latter also, and of this there is no 

 doubt, arise, although on the same metameres, still in other parts of these meta- 

 nieres. The two genera mentioned here, Pallenc and Pscudopalleiu\ also show that even if greater 

 or smaller rudiments of the embryonal legs are found in the first larval stage, these rudiments have 

 quite disappeared in the second stage, so that here no trace of limbs is found, from which a new 

 development might arise. 



The second larval stage of Phoxichilidiitiu shows, in accordance with the parasitical habits of 

 the animal, a quite particular development. I ha\-e nnself only had the first stage for examination; 

 but as this larva has repeatedl\- been the object of thorough e.xaminations, I may nevertheless, relying 

 on these examinations, give a short survey of the development of its second stage, founded on the 

 representation by G. Adlerz, Bidrag till Pantop. ]\Iorphol. 1888, especially referring to his figures 

 4 — 12 in the two accompanying plates. The second larval stage then begins with the disappearing 

 of both pairs of embryonal legs, so that only slight traces or remnants are left. After a couple of 

 moultings, during which the rudimentary remnants of the legs by and by quite disappear, the imagin- 

 al limbs are begun, in the common way and in the common order, without, however, breaking 

 through the outer, common, wrapping membrane, until all the traces of the embryonal legs have di.s- 

 appeared. Adlerz now supposes the foremost pair of imaginal fore limbs (II) i.e. the palps, to be 

 begun, cp. his fig. 10, upon which follows the further development of this pair of limbs in fig. 11 and 

 fig. 4 (pi. I); but in the first place the genus PJioxichiliduiiii as imago has upon the whole no palps 

 (onh- the ovigerous legs are found in the male), and next both pairs of fore limbs arise from the 

 lower side of the animal in the way common in Arthropoda, by the growth of a little cellular mass, 

 while Adlerz makes the extremity II develop as the other limbs of the Pycnogonida, especially the 

 ambulatory legs, by a swelling of the sides of the blastoderm or the ectoderm. According to this I 

 cannot take the small tubercles (II) on the side of the trunk to be the future ovigerous leg.s. Neither 

 can I have any great confidence in the representation or interpretation by Adlerz of the ganglionic 

 string in Phoxicliilidinni^ cp. his fig. 4, pi. I; at all events, it does not agree well with his figure of 

 the same string in A{yiiip/ioii Strocinii^ which latter figure I take to be correct. In m\- opinion the 

 ganglion ug which he interprets as nndre svselggangliet (the nether pharyngeal ganglion), and from 

 which a nerve is seen to branch off to the extremity II (it ought to be extr. Ill, as the former extre- 

 niit\- is wanting in all Phoxichilidia), nuist be the ganglion from the first segment of the trunk plus 

 the coalesced ganglia from the metameres of the embryonal legs, or, as it might also be called, the 

 nethermost pharyngeal ganglion. Accordingly I think that after the description of this larva by Adlerz 

 is neither here to be found any continuity between the second pair of embryonal legs and the ovige- 

 rous legs of the male. 



vSemper, Pycnog. und Larvenf. 1874, who, like Adlerz, takes it to be the second extremity 

 (2), i.e. the palps, which grows to a little protuberance (be>-ond which, for the rest, it never passes) 

 seeks to remove the difficulties by identifying the first pair of ambulatory legs with the completely 



