173 
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
are taken into tlie mylohyoid muscle, and do not form an accessory 
thyroid ; 
(3) The suprapericardial bodies (“ post-branchial ” of Maurer) are 
paired, developing on the right as well as on the left side of the embryo ; 
(4) These bodies lie in the plane of the second vagus cleft (fourth 
branchial beginning with the liyomandibular), and are followed by a 
third vagus cleft. Hence they cannot well be regarded as the rudiments 
of a posterior branchial cleft. 
Mechanism of Egg-laying in Frog.* — Prof. M. Nussbaum corro- 
borates Spallanzani as to the possibility of eggs being laid (by Bana 
fused) without the aid of the male, and inquires further into the manner 
in which the ova pass from the abdominal cavity into the oviduct. On 
both sides of the ligamentum triangulare hepatis and on the rima trans- 
versa hepatis the cells are all ciliated ; in the region of the M. rectus 
abdominis the naked cells occur in islands, i. e. ciliated cells pre- 
dominate ; in the region of the M. obliquus abdominis the ciliated cells 
are in scattered groups ; in the depths of the recessus pulmonalis there 
is no ciliated epithelium ; at the beginning of the oviduct there are also 
ciliated cells on the peritoneal wall ; laterally to the beginning of the 
oviduct, over the M. obliquus abdominis internus, they are numerous ; 
medianly to the oviduct there are none. 
The non-ciliated recessus pulmonalis acts as a sort of reservoir ; it 
is filled with ova and emptied by the action of the anterior part of the 
M. obliquus abdominis internus. This muscle also acts on the begin- 
ning of the oviduct, displacing it laterally, — an action resisted by the 
ligamentum triangulare hepatis. The contractions of the heart also 
help in inducing the movement of the ova. From the rima hepatis, 
however, ova may pass into the ostium by ciliary action alone. 
Early Development of Amia.f — Dr. Bashford Dean begins with an 
account of the spawning habits. In spring the fish leaves the deeper 
water, where it has remained sluggish during the winter, and moves to 
the shallows. Spawning began on April 25th, and was generally com- 
pleted by the 1st of May ; larvae were abundant by the middle of the 
month. It is said that the fish divide into spawning parties, each con- 
sisting of a female and several males. The nests of weeds and rootlets 
are prepared in advance of spawning. The fishes apparently rub closely 
together, and the eggs and milt are emitted simultaneously. The eggs 
adhere to what they touch, and there may be about a million in a nest. 
A single male mounts guard, and his breathing and restless movements 
are doubtless important in causing currents. A swarm of larvae attends 
the male for some time, and he courageously protects them. 
The early development of Amia bridges the gap between Ganoids 
and Teleosteans. In many ways it is Lepidosteoid, e. g. in meroblastic 
segmentation, relations of blastoderm to yolk, flattened segmentation 
cavity, late gastrulation, early neuron, and absence of neurenteric canal. 
The Teleostean features, on the other hand, are thus summarised : — 
Small area of blastoderm at the beginning of invagination (?) Flattened 
segmentation cavity. Early relations of inner germ-layer of dorsal lip 
* Arch. f. Mikr. Anat., xlvi. (1895) pp. 479-500 (1 pi.), 
f Quart. Journ. Micr. Sci., xxxviii. (1896) pp. 413-44 (3 pis., 13 figs.). 
