144 LACINULARIA SOCIALIS 



Now, if the view I have propounded be correct, the Rotifera furnish 

 this wanting Hnk, and connect the Echinoderms with the Nemertidae 

 and Nematoid worms. 



At the same time it helps to justify that breaking up of the class 

 Radiata of Cuvier, which I have ventured to propose elsewhere, by 

 showing that the Rotifera are not '' radiate " animals, but present a 

 modification of the Annulose type — belong, in fact, to what I have 

 called the Annuloida, and form the lowest step of the Echinoderm 

 division of that sub-kingdom. 



From our imperfect knowledge of the Nematoid worms it is diffi- 

 cult to form a definite scheme of the affinities of the Annuloida ; but, 

 perhaps, they may be sketched as in the Diagrams, PL III. [Plate i6]. 

 These diagrams represent the arrangement of the ciliated bands with 

 relation to the axis of the body in the Rotifera. 



Underneath each Rotifer is an Annelid or Echinoderm larva, \\'\\}a. 

 its ciliary bands represented in a like diagrammatic manner, to show 

 the essential correspondence between the two. 



This paper is now printed exactly as it was read before the Microscopical Society on the 

 31st of December, 1851, with the exception of those notes which refer to the very excellent 

 memoir of Dr. Leydig, published in February, 1852. Dr. Leydig must have been working 

 at the subject at about the same time as myself, in the autumn of last year ; and if I refer to 

 the respective dates of our communications, it is merely for the purpose of giving the weight 

 of indefjendent observation to those points (and they are the most important) in which we 

 agree. 



It is the more necessary to draw attention to this fact, since Professor Ehrenberg, in a late 

 communication to the Berlin Academy, hints that the younger observers of the day are in a 

 state of permanent conspiracy against his views. T. H. H. 



July 9, 1852. 



DESCRIPTION OF THE PLATES. 



The letters throughout have the same signification : — :z, trochal disc ; ^, body ; 6', tail of 

 peduncle; ^, mouth ; e, pharynx; f, " yellow mass " ; ^, gizzard ; h, " pancreatic sacs " ; 

 i, rectum ; /•, anus ; /, ovary ; in, water-vessels ; n, ganglion ; c', ciliated sac ; /, upper 

 circlet of cilia ; /', lower circlet of cilia ; ;-, vacuolar thickenings. 



Plate I. [Plate 14]. 



Laciiitdaria socialis. 

 Fig. 



1. A single individual from the side. 



2. Lateral view of the trochal disc. 



3. Trochal disc from above. 



4. Aperture of the mouth — ciliated sac and ganglion. 



5. Animal retracted. 



