PYCNOGONIDA. 



31 



three stages of the development of the larva of Ammothea {Achclia), the last one belonging to our 

 third larval stage. On the place of the imaginal fore limbs, not the embryonal legs, are here seen 

 two pairs of short, stubby appendages which I, in accordance with Dohrn, consider as the beginning 

 of the palps and ovigerous legs, that is to say, not as embryonal legs that, having been 

 reduced, now again are growing and developing, but as the imaginal fore limbs that 

 have arisen anew, and are originating in the way common in Arthropod a. To me, at 

 all events, the theory of the new formation of these limbs is no make-shift - , as Dohrn thinks 1 ) it 

 has been to Semper to enable him to homologize the Pycnogonida and the Arachnida, but I have 

 arrived at my opinion by following the development; it has, however, for me also the value to 

 diminish the difference between the number of legs in the thorax of the Arachnida and the Pycnog- 

 onida, which difference, according to what has been stated here, would only be as 6 to 5. 



Systematism. 



Before entering upon the systematic representation of the species of the Pycnogonida, I shall 

 have to say some words concerning the place of these animals in the system of the Arthropoda upon 

 the whole, a question I frequently have touched on in the preceding section. To give here a copious 

 representation of all the different opinions that have been set forth with regard to this question, would 

 only be of little use, even if it might afford some interest to see how these animals have been regarded, 

 now as Crustacea, now as Arachnida, and at last have been referred neither to one nor the other of 

 these two classes, but have been declared a particular, independent group, outside of all the four 

 classes of the Arthropoda (Kingsley, Classif. Arthrop.), nay, have even by some authors been regarded 

 as a particular, fifth class (Sars, Pycnogonidea), comp. also I hie, Phylog. Pautop. 2 ). I think that by 

 the treating of the question of the position of the Pycnogonida in the system too small regard, or, 

 most frequently, no regard at all has been paid to the developmental history. As important momenta 

 of resemblance with regard to the Arachnida, I think we may point out: 1) The proboscis of the 

 Pycnogonida, which is found in all real Arachnida, and, as in these, is only a process of the trunk 

 cp. p. 19. 2) The development of the body into two chief divisions, a thorax and an ab- 

 domen, each with its particular limbs or beginnings of limbs. — By considering the limbs 

 of the Pycnogonida the authors have always, or almost always, started from the point that the typical 



'I Dohrn, Pantop. Golf. Neap. 1SS1, p. 240, says of the theory of Semper: Dadurch aber ward er (o: Semper) 

 genothigt, fiir die dann spater bei den Mannchen, nach geraumer Latenz wircklich hervorsprossende Extremitat III (i.e. the 

 second pair of imaginal fore limbs, or the ovigerons legs) den Eiertrager, auf den Nothbehelf der -Neubildung^ zu verfallen, 

 — womit dann ebeu die ganze, auf diese Auffassung begriindete Homologisirung der Pycnogoniden mit den Arachniden 

 Banquerott machte . 



2 ) The here mentioned paper by Ihle seems to me upon the whole to be most of all a curiosity, a pregnant instance 

 of what may be the result of the loosest systematizing without the slightest personal examination. As a specimen I shall 

 cite the following passage: AIs die Ahnen der Pantopoden betrachte ich die Myriopoden, erstens weil die letzteren die 

 einzigen Tracheaten sind, welche abdominale Extremitaten besitzen, und zweitens, weil — wenn wir die Arachnoideen und 

 Crustaceen ausschliessen — , die Myriopoden die einzig iibrig bleibenden Tiere sind , von welchen wir die Pantopoden ableiteu 

 kc'mnen, sodass wir fast notgedrungen die ersteren als die Vorfahren der letzteren betrachteu mussen .... und von ersteren 

 (d: Myriopoden) haben sich selbstandig Pantopoden, Insekten und Arachnoideen abgetrenut> (1. c. p. 606). 



