ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
439 
monts, by moans of which the yolk-elements lying in the lumen of the 
enteron are actively taken up. 
The rudiments of the semicircular canals and the endolymphatic 
duct appear very early ; and the same is true of the lungs. The olfactory 
sac and the auditory apparatus are strongly developed in compensation 
for the rudimentary condition of the eyes. The teeth are developed very 
early, and before any other hard structures appear in the head; each 
tooth arises, like the placoid scales of Selachians, on a free papilla. The 
cartilaginous primordial cranium does not differ in its development from 
that of other tailed Amphibia. An indication of a fourth epibranchial 
may be made out in the visceral skeleton. 
Pronephros of Amblystoma punctatum.*— Mr. J. L. Kellogg reports 
that the first portion to appear is the segmental duct which arises from 
the somatic mesoblast. The anterior end of the duct becomes con- 
stricted off from the peritoneal epithelium, except at two points, where 
the nephrostomes are to open into the body-cavity. As the organ 
becomes older and the openings into the body-cavity are acquired, the 
nephrostomes become more and more funnel-shaped in outline. These 
nephrostomes are segmentally arranged. The glomerulus in Amblystoma 
appears much later than in the frog. 
Egg-membranes and Micropyle of Osseous Fishes.f— Mr. C. H. 
Eigenmann has examined the eggs of various osseous fishes, which he 
arranges thus : — 
I. Eggs with a single membrane, the zona radiata. 
a. Zona radiata a single layer of uniform structure. 
Notemigonus and Carassius. 
a a. Zona radiata differentiated into an inner and outer 
layer. Morone , Esox , &c. 
II. Eggs with a zona radiata and a thin homogeneous outer layer. 
b. Outer membrane without appendages. Clupea. 
bb. „ „ bearing filiform appendages. Fun - 
dulus. 
bbb. „ „ with short appendages. Pygosteus. 
III. Eggs with a zona and a thick outer layer produced by a secretion 
from, and metamorphosis of the granulosa cells. Perea. 
The author agrees with those who regard the zona as being derived 
from the yolk, and in some points confirms the statements of Kolliker. 
Development of Serranus atrarius.J — Mr. H. Y. Wilson has a pre- 
liminary notice on the development of the Sea Bass, the egg of which 
is not difficult to rear. This egg is small and pelagic, and has one oil- 
globule; in almost all segmentation is strictly regular and bilateral 
as far as the sixteen-cell-stage. When thirty-two cells are formed the 
blastoderm is no longer bilateral. By a process of excentric thinning 
out one portion of the blastoderm becomes thicker than the rest, and 
it is round a small arc of this portion that the germ-ring first begins to 
form. This ring is everywhere formed as an ingrowth of cells from the 
edge of the blastoderm, in which the superficial layer takes no part. 
* John Hopkins Univ. Circ., ix. (1890) p. 59. 
f Bull. Mus. Comp. Zool , xix. (1890) pp. 129-55 (3 pis.). 
X John Hopkins Univ. Circ., ix. (1890) pp. 56-9. 
