ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 715 



The function of the complicated nuclear division appears to be 

 that of dividing the nucleus into two comijletely equal halves ; in the 

 first segmentation the parts are often very unequal in size, and if, 

 as Heuser supposes, there are several different substances in the disks 

 of the microsomes longitudinal division would be the safest means 

 for distributing the substances equally to the two daughter-nuclei. 

 It is quite clear that tlie nucleus has a nutrient function for the cell, 

 though we do not yet know what its character is. In the internodes 

 of the Characefe we see the nucleus increasing in proportion to the 

 mass of the increasing cytoplasm, although here cell-division does not 

 accompany nuclear division ; here indeed direct division of the 

 nucleus (by constriction) takes the place of indirect division. 



Nucleus of the Auditory Epithelium of Batrachians.* — The 

 results of J. Chatin have a double interest, as affording us more 

 complete information as to several points in the comparative histology 

 of the auditory epithelium, and as bearing on the structure of the 

 nucleus. 



The study of the epithelial layer which invests the labyrinths of 

 Batrachians demonstrates a close relationship between the sustaining 

 and sensitive elements ; they are intimately connected, and they 

 undergo the same kind of modifications. What is true of Batrachians 

 is true also of other vertebrates ; in the Mammalia, for example, there 

 are auditory rods and ciliated cells, but between the two all inter- 

 mediate stages are to be made out, and this even at some single 

 point. 



As to the intranuclear corpuscles the author finds that, so soon as 

 they have acquired their definite characters and become grouped in a 

 plexus they are all perfectly identical ; there is no trace of any 

 nucleolus. In insects, Chatin has noted the inconstant character of 

 the nucleoli, and Klein, working at certain glandular elements of the 

 Batrachia, likewise bears witness to their absence. 



Epidermis of the Chick.t— C. Frommann has examined the 

 epidermis of the chick during the last week of its stay in the shell, 

 and finds in it granular cells and net-cells ; the former are rounded 

 or oval and contain granules which are fused into cords of various 

 forms ; these are connected with one another by filaments of various 

 degrees of fineness, which traverse the delicate spaces left between 

 them ; here and there, however, there are larger spaces. In neither 

 case have the spaces any special wall. The body of the net-cell is 

 traversed in all directions by a wide-meshed network ; part contains 

 neither nuclei nor any aggregations of cell-substance, while in other 

 parts the nodal points have nuclei. On the whole, the characters of 

 the cells of the epidermis are the same as after the period when the 

 chick leaves the egg. Certain differences are presented in the parts 

 of the skin which are feathered, fcjr there is there ordinarily a layer 

 of small granules imbedded in a pale, finely granular substance, in 

 which nuclei are either completely absent or are irregularly scattered 



• Ann. Sci. Nat. (Zool.\ xvi. (1884) 5 pp. 



t Jenaisch. ZeitHclir. f. NiituiwisH., xvii. (188 J) pp. 941-50. 



3 li 2 



