﻿I'VCNOGONIDA. 2^ 



of the excretory duct and tliorn in contradistinction to Baraiui Casfrlli. Hock, in Nonv. etiid. 

 Pycnog. , 1881, draws the gland with excretory dnct and thorn in Aiiimothca loiigiprs^ pi. XXX, 

 fig. 40, and in Pyoiogoniiiii littoralr , pi. XXX, fig. 45, a.s well as the gland alone in Xyiiiplion gallicuDi, 

 pi. XXX, fig. 43. 



The descriptions and figures of Dohrn, as well as most of those of Hoek do not ver_\- nnich 

 resemble those given by me; bnt I suppose that the\' generally represent a younger stage in the 

 development of the gland, whereas my figures, especialh" of the larva of Nyi)iplion i^rossipes ^ pl- Ii 

 fig. 22, and those by Hoek of Xxiiiphoii loiigicoxa^ Report Pycnog. Challenger., j^l- XX, fig. 5, which 

 figures are verv nnich alike, show the fully developed stage. 



^Morgan, in Contrib. Enibr\ol., 1891, has drawn the bvssus-glaud in the larwa of Tanystylum 

 orbiciildhi/i/, pi. IV, fig. IX, in a shape most resembling \\\\ figure of the gland in X\inpIion grossipcs. 

 Else ]\I organ does not mention the gland at all. 



I have been rather long in sijcaking of this gland , partly because it seems to me to have 

 hitherto been somewhat overlooked, and partly because I suppose it to have some morphological, 

 svstematic importance, compared with the poison-gland in the corresponding pair of limbs in the 

 Arachnida. Possibh' it might also be compared with the gland wdiich Dohrn has described by the 

 name of secretorv organ , and which he mentions as occurring in the palps and the ovigerous legs, 

 or, where these limbs are wanting, in the corresijonding metameres. I think at all events this com- 

 parison to be more obvious than the comparison with the sexual glands; comp. Dohrn, Pantop. Golf. 

 Neap. 1881, his Excretionsorgane and the following jaaragraph , Geschlechtsorgane und Eutwickel- 

 ung , p. 63 seq. 



The development of the second larval stage begins with the growing of the 

 hindmost segment of the trunk, and the separation of a foremost ring with the first 

 pair of hind limbs, or ambulator)' legs, uf)on which in a similar way the second and 

 third pairs of a m Ij u 1 a t o r y legs are separated, while the fourth pair and the can d a 1 

 segment are seen behind as a three-cleft appendage. At the close of the develo])ment 

 of this stage the embryonal legs have fallen off, but the imaginal limbs and fore- 

 limbs, the palps and ovigerous legs, have not appeared, if the)' appear at all. ( ) n 1 \- 

 very rarely the chelifori fall off already on this stage. The b\'ssus-gl and is kept till 

 the development of the stage is finished. 



The development of the second stage does not take place at once, but through more or fewer 

 castings of the skin, and in such a way, that sometimes a greater, sometimes a smaller inter\'al is 

 found between the origin and the development of each of these three pairs of ambulatory legs, while, 

 however, the consecutive order is kept. Perhaps it nia\' be called a little arbitrar\' to limit the second 

 stage in the way we have done here, as in some species so great a pause may occur during the 

 stage, especially after the development of the secontl pair of ambulatory legs, as is the case in Pstu- 

 dopallcnr circiiliiris, that -^ve might as well place the limit of a larval stage after the development of 

 the second pair as after that of the third pair; in nu)st Pycnogonid-larv;c, however, the development 

 is evenly advancing, till the third pair of aml)ulator\' legs ha\'e been de\'eloped. 



As in the preceding section the genera Palleiir and Pscudopallcnc were especialh' nientioned 



