CURRENT LITERATURE, 93 



CURRENT LITERATURE. 



Pilsbpy, H. A. — Tryon's Manual of Conchology, ser. ii, vol. xii (pt. 47), pp. 

 113 — 176, pis. xxix — xlvi, and xxxvi«. 



Mr. Pilsbry continues his account of the species of Oxystyla from Mexico, &c., 

 and then passes to the South American species, of which latter he gives a useful 

 conchological table. He then deals with Porphyrohaphe which, he points out, is 

 mainly to be distinguished from Oxystyla by the peristome being "thick and blunt 

 or reflexed" and not "thin and acute." So far as known the anatomical differences 

 appear to Vje unimportant. The concluding portion of the present part deals with 

 Liguus, in which genus — apart from Liguus, s.s.— he admits as subgenera Hcmi- 

 bulwius and Corona. The typical forms are Antillean, those of the first subgenus 

 Colombian, the residue being South American. He points out that Liguus may be 

 separated from Orthalicus and Oxystyla by the sculpture of the protoconch. His 

 very careful study of the variation of the shell in the species of Liguus will be of 

 great service to the systematise 



We note new varieties of Oxystyla pi'incejJS, 0. pulchella, and 0. zebra. — E.R.S. 



Drew, G. A. — The Anatomy, Habits, and Embryology of Yoldia limatula. Say. 

 Mem. Biol. Lab. Johns Hopkins Univ., Baltimore, 1S99, '^o^- i^i PP- I — 2>7f 

 pis. i — v. 



In one of our recent numbers we noticed a preliminary paper by Dr. Drew, upon 

 certain members of the Prviobranchia ; now we have before us the finished memoir, 

 in which the life, habits, anatomy, and embryology of Yoldia limatula are dealt 

 with at considerable length. As we have already drawn attention to the chief 

 descriptive matter of the preliminary paper, it will perhaps be more advantageous 

 here to take a somewhat broader view, and offer a few remarks upon the general 

 inferences to be drawn from the detailed facts. 



It will be remembered that Pelseneer — the author to whom we owe our most 

 comprehensive account of the anatomy of the Nuculidre — was particularly struck by 

 the close similarity of structure and primitive characteristics of the group as a whole. 

 Now the predominant note of Dr. Drew's paper is in direct opposition to this, for 

 he lays stress throughout upon the specialised character of certain organs and the 

 striking divergence in important features between the several members of the 

 family. In fact one gathers from his researches that the Nuculidcc, far from forming 

 an extremely primitive homogeneous group, are primitive indeed to a certain extent, 

 as evidenced by the structure of their gills, but have diverged so far from one 

 another in various particulars as to form a decidedly scattered assemblage, with a 

 common ancestor in the dim past, of very generalised structure. 



Apart from this general opposition to our previous ideas of the family, it must be 

 noticed that, in dealing with the same species, the accounts of anatomical structure 

 given by our author and Pelseneer are in many cases incompatible with each other, 

 and this too in features by no means trivial, such as the presence or absence of a 

 distinct pleural ganglion, of a posterior aorta, of an external opening to the otocyst, 

 and so forth. Have we here a remarkable instance of individual variation or some 

 error of observation ? If the latter be the case it seems probable that the error does 

 not lie with Dr. Drew, for in the first place his material was fresh and plentiful, and 

 in the second his general conclusions with regard to the heterogeneous character of 

 the family have been just lately supported by Stempell's study of Leda. 



With reference to the primitive nature of Yoldia, kept somewhat in the back- 

 ground throughout the paper, we should like to draw attention to a curious and 

 surely primitive condition of the nervous system. The cerebral and visceral com- 

 missures are ganglionic, and pass imperceptibly into the cerebral and visceral ganglia. 



It is interesting to note in the embryological section, which as in the preliminary 

 paper is mainly devoted to the ectodermic test, that the otoliths are formed while 



