154 Descriptions of Preparations. 



Star Fishes, p. 199 ; and Peach, Annals and Magazine of 

 Natural History, vol. xv. p. 171, 1845, for an account of one 

 of the Aspidochirotae, belonging to the British Fauna, Holo- 

 thuria nigra, which, from its constantly observed ejection of 



more or less indirectly with them as also with the exterior. And fourthly, the 

 antithesis which might be supposed to exist between Vermes and Echinodermata 

 by virtue of the chitinogenous character of the integumentary system universally 

 found in the one, and the calcificatory character of the same system as observed 

 in the other of the two sub-kingdoms, vanishes when we observe that amongst the 

 Vermes at least, the integumentary system of the same animal in both the highest 

 and the lowest orders, is competent to secrete or excrete both these chemical sub- 

 stances. All the three orders of the class Platyelminthes, the Taeniadae and 

 Trematodes (Leuckart, Die Menschlichen Parasiten, p. 475), and the Turbellarians 

 (Schmarda, Neue Wirbellosen Thiere, 1859, i., pp. si. xiii. 29), have calcareous 

 particles deposited abundantly in, as well as chitinous armature developed upon, their 

 integument. And the secretion of a calcareous vermidom by certain of the Tubicolar 

 Annelids (Serpulaceae), a family which, in their history as well as their structure, 

 appear to combine the peculiar characteristics of the sub-kingdom Vermes in the 

 most distinctive manner, points very clearly in the same direction. 



The relationship of the Rotifera to the Echinodermata is founded upon their 

 resemblance to the larval forms of these animals, and upon their possession of a very 

 well developed water-vascular system. The resemblance of the adult Rotifera, 

 which it should be borne in mind do not themselves go through any metamorphosis, 

 beyond that of attaining in some cases a few appendages wanting in the young 

 state, to the larvae of various Echinodermata and Vermes, is very clearly shown in 

 a series of semi-diagrammatic figures appended to Professor Huxley's Paper on 

 Lanicularia Socialis, in the Transactions Microscop. Society, New Series, vol. i., 

 J 853? ph 3- I^ut striking as this resemblance is, it may be said to approximate the 

 Rotifera to the Vermes as much as to the Echinodermata, and may be, by persons 

 who demur to allowing that a close parallelism exists between the two latter subjects 

 of comparison, expressed as amounting to nothing more than a permanent retention 

 by the Rotifera of certain of the characteristics of the larval state of higher Annelids. 



The affinities again of the Echinodermata to the Platyelminthes must be held to 

 be overstated by Semper, when I. c, p. 197, he speculates in a controversy with 

 Haeckel as to the 'Phylogeuie' of the Echinodermata, whether the Dendrocaelous 

 Planarian may not have been the parent stock of the Gephyrean Sipunculidae and 

 of the Echinodermata. The Platyelminthes as a class do, it is true, present a singular 

 resemblance in their developmental stages and metamorphoses to the Echinodermata ; 

 some of them possessing a pseud-embryo, as PUidium, which may compare for com- 

 plexity and importance with Bipinnaria Asterigera, whilst others have their larval 

 stages marked merely by the possession of some external ciliated integument, which 

 is got rid of by ecdyais or absorbed, and may have as direct a development as Uolo- 

 thuria tremula. To this point of resemblance maybe added the dislocation of the oral 

 orifice from the anterior eye-carrying part of the body which the Turbellarians 

 present us with, and which even in the face of the fact that in some Annelids every 

 segment of the body may carry an eye, as in Polyophthabnus, bears no inconsiderable 



