460 Bibliographical Notice. 



suggested, the presence of "nutritive-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 Grenella and Cardiunij 

 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 fur Natur- 

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

 these stages are long antecedent to the formation of mouth or 

 velum. The figures of Love*n to which I refer are those in 

 which the " Richtungsblaschen " 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 Love"n 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. 



Evenings at the Microscope ; or Researches among the Minute Organs 

 and Forms of Animal Life. By Philip Henry Gosse, P.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 



