318 TKOCHIDJS. 



regarded as isolated, and if it is to be described at all, it ought 

 to be done minutely in order to be correct. 



I prefer the finished painting to the crude outline, and so 

 with an animal or shell. I repudiate the meagre lists of 

 family, generic and specific names, devoid of description of the 

 object ; yet we find such dishonest stuff sufficient to qualify its 

 authors to head with their names a family, genus, or species, 

 or at least to figure as the "fortemque Gyan, fortemque 

 Cloanthum," in the serried ranks of worthless synonyms. 



Generalization of masses of objects of natural history is 

 always a failure ; the result is confusion and loss of identity ; 

 and though now and then an epithet too many may occur 

 in specific description, in such case a fastidious criticism may 

 perhaps be dispensed with. 



I have reserved until the termination of the descriptive 

 notes, my remarks on the branchial apparatus and reproduc- 

 tive organs of the Trochi, as I hoped, in a very few words, 

 contrary to my own doctrine, to generalize on these points. 

 I am disappointed; some anomalies have presented them- 

 selves which require further investigation. The branchial 

 plume of the larger Trochi I cannot speak of the minuter, 

 as they escape observation are acutely pointed anteally, in- 

 creasing in breadth posteally, to their arrival at the region of 

 the pericardium. In most other Pectinibranchiata the reverse 

 is the case ; but perhaps this structure has a connection with 

 the reproductive organs. The plume is usually long, tapering 

 like a leaf to a fine point, and composed of one or more rows 

 of short, drab-coloured, close-set strands, accompanied, we 

 think, in some species by the rudiments of mucous fillets. 



As regards the reproduction, I believe that the sexes of the 

 Trochi have always been considered distinct in each indivi- 

 dual ; M. Cuvier states so ; but I have failed to discover in 

 the usual position, except in the very minute species, an ex- 

 serted male organ, or a retractile one in the branchial vault, 

 or stomachal cavity : the only organ that I can find, that has 

 the least similitude to a male appendage, is a narrow, white, 

 tough, gently arcuated, pointed filament, lining or attached to 

 one of the sides of the branchial leaf, from base to point. 



