ZOOLOGY AND BOTANY, MICHOSOOPY, ETC. »',.">, 



which unite with neighbouring cells, and form cell-masses. The func- 

 tion must in all cases be regarded as the same, the cells tending to 

 check haemorrhage when the vessels sire injured. 



Kopsch figures and describes preparations which entirely confirm 

 Deetjen's results, while Argutinsky describes similar results obtained 

 during observations on tlie blood in malaria. The point emphasised by 

 all is the relation now proved to exist between the thrombocytes of 

 mammals and those of other animals. 



Minute Structure of Gills in Teleosteans* — Dr. Marianne Plehn 

 finds that each gill-lamella bears lateral alternating folds, in which 

 only the respiratory interchange takes place. Each fold is covered by 

 a one-layered epithelium, resting upon a nucleated basal membrane. 

 Beneath the epithelium is a single row of remarkable cells, correspond- 

 ing to the endothelial cells of the gill-capillaries. These cells are con- 

 nected together above and below, but leave in the middle intercellular 

 spaces in which the corpuscles of the blood slowly circulate, apparently 

 under considerable pressure. The endothelial cells themselves seem 

 highly plastic and yielding, so that the corpuscles are capable of foicing 

 themselves between them, and so producing different appearances in 

 surface view, according to the degree of turgidity of the gill. There 

 is however never a continuous path for the blood, but always an inter- 

 rupted network of corpuscles among the endothelial cells. A similar 

 form of capillaries has been described in the lung of Proteus. 



Minute Structure of Cartilage. f — Josef Schaffer has studied the 

 cartilage of the tail in Ammoceetes and the adult Petromyzon, and finds 

 that, in its first rudiment, the cartilage is a syncytium. It consists of a 

 honeycomb of cells, the spaces containing nucleated corpuscles and 

 themselves constituting the future ground-substance. This prochrondral 

 ground-substance undergoes microchemical change, and becomes the 

 protochrondral ground-substance. Growth of the cartilage takes place 

 both by intussusception and by apposition, owing to the conversion of 

 neighbouring indifferent cells into perichondrium. The periaxial sup- 

 porting-tissue in the vicinity of the tail-fin exhibits a peculiar vesicular 

 form. Its cells in part become hyaline and fat-containing, and between 

 them there develops a fibro-rncmbranous matrix containing indifferent 

 cells. The proximal ends of the cartilaginous rays develop at the 

 expense of this v( sicular supporting-tissue. The so-called capsules — 

 differentiations of the matrix — first appear in Pctromijzon • Jiuviatilis, and 

 arise from the cartilage cells, just as the rest of the matrix does. Other 

 differentiations of the matrix crive rise to different modifications of 

 cartilage in the adult. 



Position of Centrosome in Resting Cells.J — Prof. 0. zur Strasseu 

 finds that, at each resting stage in the segmenting ova of Ascaris, the 

 centrosome lies in the axis of the cell near its distal pole, i.e. between 

 the nucleus and the centre of the exposed surface of the blastomere, and 

 that this position is always attained, though it may involve a considerable 



* Zool. Anzeig., xxiv. (1901) pp. 439-43 (5 figs.). 



+ ZeiUchr. wis*. Zool., lxx. (1901) pp. 109-70 ('2 pis.). 



X Arch. f. Entwickmech., xii. (19'U) pp. 134-01. See Anier. Nat., xsxv. (1901) 



pp.780-1. 



