Digest of Current Literature. 323 



some good suggestions about collecting, preparing and preserving them. 

 There is a full-page plate, illustrating some useful apparatus for col- 

 lecting and transporting these plants. NOTE ON THE PASSAGE OF 



THE Eggs from the Ovaries of Batrachians, by F. Henneguy. — 

 The eggs leave the ovaries of Batrachians in a manner which is quite 

 distinct from that common in other vertebrates ; the peritoneal envelope 

 of the ovary becomes ruptured at the center of each ovule capsule, and 

 the ovules escape. After the passage of the eggs, the external surface of 

 the ovary is pierced with minute orifices which become very apparent when 

 it is stained by carmine. It is probable that the &^^ is forced from its 

 capsule by the contraction of the latter, but thus far the presence of mus- 

 cular fibers in this has not been demonstrated. Diatoms from 



THE ACHIPELAGO OF THE East INDIES, by Dr. P. T. Cleve. On 



Microscopical Preparations, by Dr. J. Pelletan. — This is a letter 

 which it would be well for those who are mounting specimens for the 

 microscope to read with care. The uselessness of a very large proportion 

 of mounted objects for purposes of study is well known. Dr. Pelletan 

 says : " They are often very pretty, placed upon a choice glass, in an 

 irreproachable cell, with varnishes of all colors," etc., but the objects are 

 without intrinsic value. " Certain preparations in Cryptogamic Botany, 

 have some value ; certain sections, dissections, or dissociations relative to 

 vegetable anatomy, thin sections of hard bodies, animal tissues, minerals, 

 vegetables, principally sections of wood, are very instructive, but among 

 the other classes of preparations the nomenclature of which fills the cata- 

 logues, it is only by hazard that one meets with an interesting slide." " The 

 more expert, prepare immense insects, or enormous Arachnides, entire, 

 after having removed their contents ; some are so very skilful that they 

 make preparations of really magnificent aspect. But, unfortunately, the 

 tegument alone is preserved, and the traces that remain of the internal 

 organs are filled with a uniformly transparent mass, in which the micro- 

 scopist finds nothing to study." We cannot quote further from this 

 article, hut we commend its perusal by all who- desire to mount objects for 

 study." 



^^{April, /<?7p).— Organization of the Zooloc;ical Service.— 

 An extract from a work of M. Dormadieu, having particular relation to the 

 the microscopical part of the service. The principal subject of interest is 

 a working table, very elaborate in its arrangement. It is illustrated both 

 in perspective and by a sectional view, but no proper idea of it can be 

 obtained except from a more complete description than we are able to 

 give. Clear Working Distance, by R. B. Tolles. Hydras- 

 tin, by Dr. John King. — Some remarks about preparing the crystals of 



this alkaloid for the polariscope. The Use of Collodion for 



Making Microscopical Sections, by Mathias Duval— The use of a 

 solution of gum, solidified by alcohol, as an imbedding material is well 

 known, and it is undoubtedly very useful for certain objects. But when 



