PYCNOGONIDA. 
SY 
three «stages» of the development of the larva of Ammothea (Achelia), 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 Arthropoda. To me, at 
all events, the theory of the new formation of these limbs is no «make-shift», as Dohrn thinks?) 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 shail 
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 Ihle, Phylog. Pantop.7). 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 ofgthe 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 
1) Dohrn, Pantop. Golf. Neap. 1881, p. 240, says of the theory of Semper: «Dadurch aber ward er (J: Semper) 
genåthigt, fiir die dann spåter bei den Månnchen, nach geraumer Latenz wircklich hervorsprossende Extremitåt III (i. e. the 
second pair of imaginal fore limbs, or the ovigerous legs) den Eiertråger, auf den Nothbehelf der «Neubildung>» zu verfallen, 
— womit dann eben 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: «Als die Ahnen der Pantopoden betrachte ich die Myriopoden, erstens weil die letzteren die 
einzigen Tracheaten sind, welche abdominale Extremitåiten besitzen, und zweitens, weil — wenn wir die Arachnoideen und 
Crustaceen ausschliessen —, die Myriopoden die einzig iibrig bleibenden Tiere sind, von welchen wir die Pantopoden ableiten 
kånnen, sodass wir fast notgedrungen die ersteren als die Vorfahren der letzteren betrachten miissen .... und von ersteren 
(ga: Myriopoden) haben sich selbståndig Pantopoden, Insekten und Arachnoideen abgetrennt» (1. c. p. 606). 
