138 ON THE STRUCTURE AND 



lowest Cmstaceans cannot escape recognition. In the Rotifera it consists 

 simply of a cerebral ganglion, with branches radiating from it ; there is 

 no abdominal chord, nor any chain of ganglia. But is the nervous system 

 of the Lophyropoda more developed? In the Dapbniae, even, we are 

 acquainted only with a cerebral ganglion and nerves proceeding from it ; 

 and, consequently, know of no grounds upon which to establish the law, 

 that a central nervous system, consisting of a ganglionic ring surrounding 

 the pharynx, and of a chain of abdominal ganglia proceeding from it, 

 belongs to the Crustacea as a fundamental character. 



Moreover, the manner in which the sensitive nerves terminate peripher- 

 ally in the Rotifera corresponds precisely with what I have described, 

 regarding this point, in the Crustacea and Insecta ; and nothing like which 

 is at present known to exist in the class " Vermes." Lastly, I shall not 

 repeat at length, but merely remark, that the eye-spots aj^parent on the 

 nervous centre of the Rotifera approximate most closely to the similar 

 structures of the Crustacea, as Ehrenberg has not failed to indicate. 



The disposition and texture of the alimentary canal, in an inquiry into 

 the systematic position of the Rotifera, alTord no decisive evidence in 

 favour of one view or the other, since many Annelids also have a complex 

 horny masticatory apparatus ; still, with respect to this I would remark, 

 that the masticatory apparatus of young Daphrdoe (I have examined, for 

 this object, the deep yellow-red young of a very large species, Daphnia 

 trutxima ?) presents a pretty close similarity with that of many Rotifers, 

 inasmuch as the two opposed jaws expand into a plate, which is toothed 

 with numerous transverse ridges, exactly like the corresponding plate in 

 Lacinularia. 



The glandular lobate appendages placed upon the stomach in the Cirri- 

 peds, which have been explained as " salivary glands," might, perhaps, be 

 regarded as analogiies of the ventricular glands of the Rotifera. Similar 

 organs, however, also exist in many of the dorsibranchiate Annelids ; 

 many Annelids also, like many of the lower Crustaceans, are alike in the 

 circumstance that the liver is represented simply by large cells, with 

 peculiar contents, situated in the wall of the stomach or intestine. Should 

 any one find an objection to the arthropodous type in the deficiency of an 

 intestine in some Rotifers {Notommata anglica, N. Sieboldii, &c.), he may 

 recall the neuropterous larva of Myrmeleon, in which, as is well known, 

 the ffeces are also discharged by the mouth ; the rectum being transformed 

 into a spinning organ. But with respect to the intestinal tract of many 

 Rotifers (as Euchlanis, Stephanoceros, Sec), what especially recalls the 

 condition of that part in the lower Crustacea, is its peculiar bell-like 

 movement, which is precisely similar to that with which we are acquainted 

 in the intestine of certain parasitic Crustaceans {Achthenes, Tracheliastes, 

 &c.) 



As to the substance which I have pronounced to be a urinary secretion, 

 the close relations which obtain, with respect to it, between the Rotifers 

 and the larva of Cyclops, cannot fail to be recognised ; whilst anything 

 allied to it is wholly wanting in the Annehds. 



Lastly, the anatomical and i3hysiological phenomena relating to the 

 sexual life speak loudly enough in favour of the proj^osition that the Roti- 

 fers should be ranked with the Crustacea. I would not lay much stress 

 upon the circumstance that they produce two kinds of ova, — the so-termed 

 " summer" and " winter-eggs" (the latter in Triarthra, in the structure 

 of their shell present much similarity with the ephippian eggs of Daphnia), 

 or that many species carry their ova about with them ; for, as regards 

 these particulars, the genus Clepsine among the Annelids might be named 

 as one in which the same thing takes place. The colourccl oil-globules 



