SYSTEMATIC POSITION OF THE ROTIFERA. 139 



also, met with in tlie vltellus of many Rotifers, and indicative of a Crus- 

 tacean type, may be left out of consideration. But of greater importance, 

 perhaps, is the striking analogy existing between the male Rotifers — 

 which in a certain sense may be said to be aborted — and those of many 

 Crustaceans. Who will not remember the diminutive, male parasitic 

 Crustaceans, which Nordmann discovered on the female individuals of 

 Achtheres, Brachidla, Chondracant/ms, and AnchoreUa, and Kroyer in 

 other Lernasopoda and Lerneae ? 



And the reason that we are only just beginning to become acquainted 

 with separate males of Rotifers is probably due to the same circumstances, 

 — appearance at a certain time of year, diversity of figure from that of the 

 female — as those owing to which we have not yet discovered the males, 

 for instance, of Ergasilus, Polyphemus, Limnadia, Ajms, &c. 



If the development also of these creatures be regarded, it will be found 

 in favour of our view ; for, with respect to several species, it has been 

 shown that the young, at its liberation from the ovum,, has not got the 

 form of the adult animal, and, consequently, must undergo a metamor- 

 jihosis. And is not the subsequent diminution, and even complete dis- 

 appearance of the eyes, which exist in the young condition of the animal, 

 a farther indication of an approach towards certain Crustacean forms? 



Whilst the structural conditions hitherto mentioned more or less power- 

 fully support the view of the Crustacean nature of the Rotifera, they are, 

 on the other hand, separated from the Crustaceans by the condition of the 

 respiratory organs and the presence of vibratile cilia, and approximated to 

 the Annelids ; but in both these respects they equally approach the 

 Echinodermata ; for, as has been said above, the proper vibratile organs of 

 Synapta digitata appear to me to be structures equivalent to the " vibra- 

 tile organ" of the Rotifer. 



But in the determination of the systematic position of an animal, the 

 question must depend, as it seems to me, upon the fact, whether the sum 

 of the resemblances is greater than that of the differences, as respects the 

 animal groups with which the animal might be supposed to be associated. 

 In applying this law to the subject under discussion, we find that the 

 number of conditions allying the Rotifers with the Crustaceans far exceeds 

 that of the properties possessed by them not in common with the Crus- 

 tacea. I consequently regard it as fully justifiable to rank the liotifera 

 as a speckd order of Crustacea, and propose, from the distinctive character 

 exhibited in them, to denominate them "ciliated Crustaceans" (Wimper- 

 krabse). They necessarily stand at the commencement of the Crustacean 

 class ; since, in the structure of their respiratory organs, they continue to 

 be allied with the Annelids. Huxley (1. c.) has regarded them as Annelids 

 possessing permanently the form of the Echinoderm-larva, and has ex- 

 pressed this comparison in diagrammatic figures (I. c, Plate HI.), in 

 which he places Lacimdaria opposite an Annelid larva, Melicerta opposite 

 to that of Asterias, Philodina to that of Holothuria, Brachionus to the 

 larva of ^ip>unculus, and, lastly, Stephanoceros to the larva of Echinus. 

 Although the ingenuity of this attempt must be admitted, still I am 

 unable to adopt the view of the English observer, but am compelled, from 

 the considerations above detailed, to declare myself an adherent to Bur- 

 meister's view, as the only one agreeing with my own. 



CLASSIFICATION OF THE CILIOCRUSTAGEA. 



It is obvious that the arrangement of the Ciliocrustaceans, or Rotifers, 

 as proposed by Ehrenberg, must be changed, inasmuch as the principle 



