460 BihliograpMcal Notice. 



suggested, the presence of "nuti-itivc-yelk" particles is very 

 probably a disturbing factor in the early stages of recapitulative 

 development ; and I hope by the application of this hypothesis 

 that some further results of a definite kind may be attained. 



Meanwhile I beg to assure Prof. Salensky and other doubters 

 that the primitive endoderm does arise by invagination in the 

 Mollusks cited by me, as there will, I hope, shortly be evidence 

 to show in the form of careful drawings. 



The drawings of Loven of embryos of Crenella and Cardium^ 

 which clearly indicate a diploblastic phase brought about by in- 

 vagination as I have followed it out in other Mollusks, are not 

 in the least degree elucidated or touched by Prof. Salensky's 

 figures of young Ostrea in the paper in the ' Archiv ftir Natur- 

 geschiclite.' There is no question whatever about the mouth : 

 these stages are long antecedent to the formation of mouth or 

 velum. The figures of Lov^n to which I refer are those in 

 which the " liichtungsbliischen " is seen escaping from the 

 mass of cells, and in which an orifice is marked as the orifice 

 at which the " Richtungsblaschen " escape. This orifice is, I 

 am persuaded (by analogy with fully worked-out examples in 

 other Mollusks), the orifice of invagination of the Gastrula- 

 endoderm, and not connected with the " Richtungsblaschen " 

 as Lovdn supposed. 



Let me, in conclusion, point out that the publication of 

 figures to illustrate such observations as those which now 

 have to be made, on embryological matters, is in this country 

 a terribly lengthy and tedious affair, and that naturalists must 

 have some patience and consideration for one another under 

 the infliction. 



BIBLIOGRAPHICAL NOTICE. 



Eveninrjs at the Microscope ; or Researches among the Minute Organs 

 and Forms of Animal Life. By Philip Henry Gosse, F.R.S. A 

 new edition. 8vo. London : Society for promoting Christian 

 Knowledge, 1874. 



This little book of Mr. Gosse's (a writer whom one is always pleased 

 to meet in the field of natural history) is intended as a guide to 

 those who, possessing a microscope, are desirous of using that in- 

 strument as a means of obtaining something more than mere passing 

 amusement. It is founded for the most part upon his own observa- 

 tions, or at least upon observations practically verified by himself, a 

 circumstance which gives it a very different character from that of 

 most of the compilations which aim at popularizing natural history. 

 The author's plan is a very admirable one. Instead of going out 

 of his way to describe and figure objects whose great interest is 

 their rarity, he sticks almost throughout to those common forms 



