HARD WICKE' S S CIENCE- G O SSIP. 



131 



of all the great naturalists, and competent to set forth 

 in a pithy and attractive style their best thoughts, 

 theories, and hypotheses, ought to be acceptable to 

 that increasingly large circle of readers who are 

 interested in all the great geological and biological 

 questions of the day. The large scope of Mrs. 

 Bodington's prettily got-up and well-printed book 

 will be gathered from the titles of the following 

 chapters: "Some Curious Facts connected with the 

 Evolution of the Eye ; " " The Mammalia, Extinct 

 Species and Surviving Forms;" "The Flora of the 

 Past ; " " Interesting Facts in Evolution ; " " Micro- 

 organisms as Parasites ; " " Puzzles in Palaeontology ; " 

 "The Air-bladder of Fishes considered as a 

 Degenerate Lung ; " " Neo-Lamarckism ; " and 

 "The Origin of the Fittest." Mrs. Bodington's 

 thoughtfulness for her readers is further exemplified 

 by the admirable glossary at the end of her delightful 

 little book. 



Proceedings of the Literary and Philosophical 

 Society of Liverpool (London : Longmans & Co.). 

 Vols, xli., xlii., and xliii. It is a pity these valuable 

 papers are not bound uniformly. Vols. xli. and xlii. 

 are in a good roan cloth binding, whilst xliii. is in 

 paper, and of a different size. We have observed 

 this lack of bibliophilic continuity before. There 

 are few of our provincial scientific and literary 

 societies which stand higher, or possess a greater and 

 unbroken antiquity than that of Liverpool. Its 

 annual volumes are always interesting — sometimes they 

 are even important. The papers they contain range 

 over a large area of literary and scientific surface, and 

 are often written by men of light and leading in both 

 literary and scientific circles. Thus, in vol. xli. we 

 have papers by Prof. Herdman, R. J. Harvey 

 Gibson, Isaac Roberts (on "Stellar Photography"), 

 Eli Sowerbutts, H. H. Higgins, T. J. Moore, 

 Fletcher-Williams, G. H. Morton, etc. In vol. xlii. 

 other papers, etc., by H. H. Higgins, T. P. Kirkman 

 (the sworn foe of poor Herbert Spencer), W. F. 

 Denning, J. E. Gore, T. F. Heyes, C. E. Brewster, 

 etc. Vol. xliii. includes papers by the Rev. T. P. 

 Kirkman, Dr. Newton, Isaac Roberts, H. H. 

 Higgins, Dr. Nevins, James Birchall, Principal 

 Rendall ("The Cradle of the Organs"), etc., etc. 



THE NEW HYDROBIA. 



IT is a hard case when any one is asked to define 

 precisely what is the difference between a 

 species and a variety. Both terms are to some great 

 extent arbitrary, and every systemalist has his own 

 notions of them, so that their needs must be more or 

 less confusion. Perhaps this is nowhere better 

 shown in the conchological world than in the dis- 

 cussion which has ensued over this so-called new 

 hydrobia between Mr. Marshall and Mr. Smith, in the 

 recent numbers of the " Journal of Conchology." Mr. 

 Jenkins has placed these views together in an article 



which appeared in the May number of this journal. 

 But in such a question I am of the opinion that a 

 certain amount of comparison with other varieties of 

 species should be taken into account, especially when 

 the conditions under which the hydrobiae live are taken 

 into consideration. Evidently H.Jenkinsi — Mr. Jenkins 

 kindly sent me specimens — approximates nearer to 

 H. ventrosa than to H. similis, and is either a variety 

 of the former, or else a new species. Mr. Marshall 

 considers it to be a variety ; Mr. Smith, on the other 

 hand, thinks it to be a new species. As it is nearer 

 to H. ventrosa the differences as enunciated by Mr. 

 Smith concern us. He says that these are "(i), in 

 habit ; (2), length and form of tentacles ; (3), colour 

 of the foot and head, and (4), in the greater size and 

 more robust form of the shells," ("Journ. Conch." 

 vol. vi. 18S9, p. 145). On these several headings I 

 would like a few words. " Habit " may be an 

 expression simply and solely of changed conditions, 

 or in other words, of varietal rank merely. And 

 under this "habit" the other differences enunciated 

 may be considered. " Length and form of tentacles, 

 colour of the foot and head, and the greater size and 

 more robust form of the shells," may all be due 

 to these changed conditions or "habit." Taken 

 separately, each of these distinctions which are given 

 as specific are merely varietal. "The greater size 

 and more robust form of the shell " occur together in 

 many species as varieties : instance, B. tentaculata v. 

 ventricosa (Menke), L. auricidaria v. magna (Colb), 

 L. palustris v. obesa (Taylor), H. pomatia v. gesneri 

 (Hartm.), H. aspersa v. globosa (Moq.), H. nemoralis 

 v. ponderosa (Malm), H. arbustorum v. conoidea 

 (Westrl.) among others. "The colour" is also 

 varietal ; many of our species vary much in body 

 colour, and it is well known that colour is never 

 specific in any case, whether of body or shell. Take, 

 for example, the slugs, and L.pere^ra, of which, rightly 

 or wrongly, varietal names have been given to the 

 various body colours. " Length and form of tentacles " 

 are of minor importance, and even do not indicate 

 varietal rank, let alone specific. Many examples of one 

 species vary much in the length and shape of their 

 tentacles. Thus I am inclined to believe, with Mr. 

 Marshall, that so far as these specimens have been 

 examined, they are varieties of H. ventrosa, and are 

 not entitled to rank as a true and distinct species. 

 But I would like to point out that in neither case has 

 there been any mention of their internal anatomy. 

 That is the only criterion which would once for all 

 settle the dispute. If they do not differ in anatomy 

 from H. ventrosa, then are they surely varieties of that 

 species ; if indeed they do differ, then are they as 

 surely a distinct species. At the conclusion of his 

 very interesting and instructive paper, Mr. Jenkins 

 mentions that our Dreissena polymorpha originally 

 came from America. This is new to me, and I have 

 always been prone to regard them, in common with 

 many other conchologists, as members of the old 



