ZOOLOdY AND BOTANY, MICROSCOPY, ETC. 215 



known as glandular cells. It is pointed out that each cell consists of 

 a lower portion from which a short stalk or process is given otf, and 

 of an upper or neck-like portion ; in frogs and toads this upper end 

 is filled with a soft finely granular matter, but in the land salamander 

 there is a body which looks like a cork to the tube. These organs 

 are not distributed over tlie whole of the body, but are specially 

 developed on the ventral side of the larva. They vary somewhat in 

 size, and are pyriform in shape ; their protoplasm is rather more 

 coarsely granulated than that of the surrounding cells, and around 

 the nucleus there is a cavity ; in larvte 25 mm. long there were no 

 filaments, but only a slightly conical process, which has the appearance 

 of a soft substance, and exhibits longitudinal striation. As the legs 

 begin to appear the cone becomes reduced, the orifice diminishes in 

 size and a rounded soft "cork" appears. Prof. Leydig again insists 

 on the relation of sensory to glandular cells, and concludes by 

 recommending a special study of the structure and metamorphoses of 

 the epidermis of the tadpole and the frog. 



Cells of the Vitreous Body.* — Herr H. Virchow finds in the merino 

 sheep that there are richly branched cells with one or several nuclei 

 on the surfaces of the vitreous body ,* they are regularly distributed 

 over the whole surface, and form a single layer. In the fowl there are 

 delicate cells which are either fibrillar or spindle-shaped ; some have 

 several processes and form a single layer over a large part of the surface 

 of the vitreous body ; these were found in two fowls, but were absent 

 from a third and from three ducks. In the frog there are (1) cells 

 with a wide delicate body, as a rule connecting two vessels ; they 

 are cells which are formed adventitiously on the outer side of the 

 vessels ; (2) granulated cells which are either rounded or elongated ; 

 (3) round cells with a round nucleus and a small quantity of proto- 

 plasm (? leucocytes) ; and (4) polymorphous cells (? also leucocytes) 

 which are either broadened out into thin irregular plates, or produced 

 into thin processes. 



Nucleiof Secreting Milk-gland Cells.t— Since according toHam- 

 marsten, casein is a nucleo-albuminate, and since nuclein is, as far 

 as is yet known, confined to the nuclei, Herr F. Nissen was led at 

 Heidenhain's suggestion to investigate the behaviour of the nuclei 

 during milk-secretion. His research has revealed the interesting fact of 

 the degeneration and disruption of the nuclei, which, therefore, in all 

 probability go to form the casein of the secretion. Within the milk- 

 cells the nuclei are observed to multiply, perhaps indirectly, since, 

 in hundreds of preparations, no mitosis was seen. The nuclei towards 

 the inner end of the cell separate themselves ofi^, surrounded by a 

 portion of the protoplasm, and, in the lumen of the alveoli, or less 

 frequently in the cells themselves, undergo degeneration. The 

 normal nuclear structure disappears, the chromatin collects in 

 separate segments at the periphery, and the segments break up into a 

 coagulation. The result is probably the casein of the milk. Herr 



* Arch. f. Anat. u. Physiol. (Physiol. Abth.), 1885, p. 563. 

 t Arch. f. Mikr. Auat,, xxvi. (1886) pp. 337-42 (1 pi.). 



