CHANGES IN REPRODUCTIVE CELLS OF ELASMOBRANCHS. Pata 
testes with glacial acetic acid,and washing quickly in water, by 
tearing up the fresh material in acetic carmine, by fixing in 
a 2 or 8 per cent. solution of formic aldehyde, by the use of 
Carnoy’s fluid, and last but not least, by a formic acid method 
which I hit on quite by accident. This consists in placing 
small fragments of the living testis in a 50 per cent. solution 
of formic acid for a few seconds, and then transferring directly 
to 50 per cent. alcohol, after which they are treated for 
sectioning in paraffin, in the usual way. By this means the 
chromosomes were in some cases rendered admirably distinct, 
but the fixation, so far as I have yet tried it, renders the 
material difficult to stain. 
Although the cells of these different kinds of fish examined 
necessarily differ somewhat inter se, the differences do not 
appear to be of any morphological importance, and the following 
description, although taken more especially from those of 
Scyllium canicula, is, so far as I am aware, applicable to 
them all. 
II. The Resting Cells in the First Spermatogenetic 
Period. 
8. The successive generations of the smaller and smaller 
cells which gradually fill up the testicular ampulle during the 
first spermatogenetic period are all alike, and I find no essential 
difference between their structure and that of the single em- 
bryonic elements (fig. 1) budded off into the stroma from which 
they gradually arise. 
The chromatin is dispersed as a coarse reticulum throughout 
the interior of the nucleus, and is not in the least specially 
related to its surface; in fact it is really denser towards the 
interior than at the periphery, and contains a large oval or 
flask-shaped nucleolus, generally attached to the nuclear wall . 
(figs. 2, 11, 12, n.). 
The chromatic threadwork itself is composed of innumerable 
staining granules, embedded in a scaffolding of clearer sub- 
stance (linin) (fig. 12), and the unoccupied nuclear space is 
filled up with a thin nuclear sap. 
