﻿i8 



PYCNOGONIDA. 



free joint is round and slender, and the second, or outermost, joint is always still thinner, most fre- 

 quenth- claw-shaped, and of about the same length as the preceding joint; sometimes, however, this 

 second joint is prolonged to a long, thin thread more than twice the length of the body, as for inst 

 in Plwxichilidium fciiioratuin, pi. I, fig. 4. The growth of the embr)-onal legs soon ceases, and even if 

 they, as is often the case, are kept in the following larval stages, they show no alteration. 



The proboscis, like the embryonal legs, begins as a low protuberance, soon growing into 

 a conical process with more or less tapering sides, but without trace of any inner or outer division, 

 far less of a coalescing of constituent parts. Tlie pharynx, however, is early developed, already in 

 this larval stage, and it is seen as a dark line stretching from the point of the proboscis towards its 

 base, as in Xyiiiphou longifarsc, pi. II, fig. 20, and in Xyinphon macronyx , pi. II, fig- 9- Tlie chitinous 

 ridges serving for the insertion of the Musculi retractores of the pharynx, are also early developed. 



With regard to the interpretation of the proboscis I shall take the liberty to state m\- opinion 

 already in this place, although my interpretation is chiefly due to the structure of this organ found 

 in a much more advanced stage of development and especially in the imago. It is the unhappy note 

 by Latreille to his description of the Pycuogonida, Regne animal, ed. II. Tom IV (1829) which is 

 found again and again. The note. I.e. p. 276, note 3, runs thus: 'Le siphon . . . m'a offert des sutures 

 longitudinales, de maniere qu'il me parait compose du labre, de la languette et de deux machoires, le 

 tout sonde ensemble . It was to be thought that Dohrn") had succeeded in demolishing this notion, 

 and I can with all my heart agree with him, when in ■ Pantopoden des Golfes von Neapel* (1881) he 

 says: «Wir wiirden . . . keinenfalls aber an eine Verschmelzung von extremitatenartigen IMundtheilen 

 zu denken haben , I.e. p. 109. We find nevertheless that Adlerz in his fine little essay. Contributions 

 to the Morphology of the Pantopoda (Bidrag till Pantopodernes Morfologi ; (1888)) tries to maintain 

 the old view of Latreille. Adlerz foimds his arguments especially on the fact that the two low- 

 ermost eantimeres (Dohrn) of the proboscis receive nerves from special centra in the first abdominal 

 ganglion , comp. his fig. 2 on pi. I , and the letters a and itg in this figure. For these two foremost 

 centra with their fibrillous punctuous mass: (Leydig: Punktmasse) in connection with the two 

 pairs of centra behind them in the same ganglion should show, how this ganglion is composed of 

 three original pairs of ganglia, but it is well known that to each pair of ganglia belongs a metamere 

 with a pair of limbs, which metamere could not then be an\thing but the two lowermost <antimeres» 

 I.e. p. 10. To this is to be answered that, as no trace of limbs has ever been seen that might corre- 

 spond to or be merged in the two antimeres, as little has any trace been found of a pair of foremost, 

 free ganglia; besides it has to be remembered that the supply of nerves for the two lowermost meta- 

 meres most properly must be said to arise from the foremost one of the two, originally separated, 

 but now coalesced pairs of ganglia, in which, but not until a later stage, the corresponding foremost 

 pair of centra have developed. This view would also agree with my examinations, as I have also 

 found the ganglia to be originalh- uniform, and not until later showing distinct centra with their 

 fibrillous punctuous mass running into or stretcliing into the nerves of the limbs. I thiiik upon 

 the whole that as to the morphology too great stress is at present laid upon the ganglia, and my 



>) Already Zenker in • Untersuchungeu iiber die Pycnogoniden» (1852) has p. 3S3 seq. rejected the supposition of 

 Latreille, referring to the representation given by Kroyer of the occurrence of the proboscis in Uie young lar\-a. 



