ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 39 



lias done an invaluable service to English students in providing this 

 translation. From many points of view it is by far the best work 

 that can be put into the hands of a zoological student. 



B. INVERTEBRATA. 



Eyes of some Invertebrata.* — J. Carriere, after pointing out the 

 different methods by which an optic organ is developed among animals, 

 and describing in detail the eyes of Musca and of Leptodora hyalina 

 as the two extreme forms of the fan-shaped eye, gives a short notice 

 of the fan-shaped eyes of Lamellibranchs. These are simplest in 

 Area and Pedunculus, where they consist of a small number of large 

 cells of the form of an elongated cone, with the point directed inwards ; 

 there is pigment peripherally, which forms a sheath for the cell-body. 

 In Area every cell has a kind of lens formed by its cuticular border. 

 The optic cells are not sharply distinguished from the epithelial cells 

 of the mantle, but are connected with them by a number of stages ; 

 these eyes, therefore, as much as those of Patella and of the ocellate 

 Medusae, " may be classed among the most beautiful examples for the 

 study of the origin of the organs of sight by the modification of 

 epithelial cells " ; while they afford yet another proof of the truth of 

 the doctrine that similar organs of sight in different classes and orders 

 of the animal kingdom may originate independently, and in fact may 

 still originate without in any way implying that such eyes have been 

 inherited from a common ancestor. 



Indestructible Infusorial Life-t — J. Hogg describes some further 

 experiments he has made on this subject, supplementing those pre- 

 viously recorded on Eotifers. Some Ciliata and Tardigrada have 

 been included, and these have, although not to the same degree, 

 exhibited a remarkable tenacity of life. The intervals of sleep and 

 vigorous life have likewise been brought into strict accord with the 

 durations of dry and wet periods of the year, so that the subjects of 

 the experiments have been kept in a perfectly dry condition during 

 the whole of the long drought which characterized the past summer. 



Moreover, some older dried specimens were subjected to an 

 artificial process of desiccation. They were kept for a time in a hot- 

 air chamber, the heat in which was raised to 200° F., and sub- 

 sequently the miniature aquarium in which they were inclosed was 

 plunged into a freezing mixture. Neither process killed them nor 

 greatly diminished their vital powers, their revivification in both 

 cases being somewhat delayed. Certain toxic agents known to exert 

 a baneful influence over higher animals were added to the water 

 supplied to the rotifers, but in no way did they produce discomfort ; 

 on the contrary, portions were taken into the stomach and partly 

 digested. On the other hand, a drop of sewage water caused marked 

 discomfort; they immediately retracted their rotating organs and 



* Quart. Journ. Micr. Sci., xxiv. (1884) pp. 673-81 (1 pi.), 

 t 'Times,' January 5, 1885, p. 4. See also further letter, Engl. Mech., xl. 

 (1885) p. 430, and criticism, ibid., p. 452. 



