'S^nL.'fJcT^^^^^^^^ of the Ovum of the Pike. 195 
9.30 A.M. — Two otoliths, or small ear-stones, were seen in 
the auditory capsule. The little bodies in c, Fig. 20, are otoliths. 
9.45 A.M. — There are indications of two arches forming, passing 
along in the situation of the future branchiae (d, Fig. 20). 11.15 
P.M. — The embryo has grown completely round the yelk, and the 
head now touches the tail. 
21s^ April, 8th day : 5 p.m. 175 hours. — I found one of the 
eggs hatched. I had not counted the number of eggs under obser- 
vation, but find included in the following catalogue 465. Many 
besides these became addled (being opaque white instead of semi- 
transparent yellow), and offensive to the nose. These were removed, 
so that we may estimate the whole of them, in round numbers, at 
500. The hatching extended over five days ; the majority being 
hatched on the 23rd April, being the tenth day after fertilization. 
On the 14th April I took 500 eggs. 
21st, or 8th day, were hatched 12, or 2*4 per cent. 
22nd „ 9th „ „ 143 „ 28-6 „ 
23rd „ 10th „ „ 197 „ 39-4 „ 
24th „ 11th „ „ 97 „ 19-4 „ 
25th „ 12th „ „ 16 „ 3-2 
add, 35 addled, 35 „ 7-0 
500 100 
The fish made their exit from the shell, some with the yelk-bag 
first, some with the tail, the majority with the head : their escape 
was effected by means of forcible, wriggling contractions of the body. 
After their exit, some lay motionless at the bottom of the vessel, 
whilst others, applying the muzzle to the leaf of a water-plant, 
adhered to it by means of an adhesive material secreted by a gland 
in that situation, and so hung, suspended from the leaf. This adhe- 
sive matter was gradually drawn longer and longer by the weight 
of the fish, until a thread as long as the little fish itself was formed. 
Adhesion was seen to be instantaneously effected upon application 
of the tiny muzzle to the leaf; sometimes there might be seen a 
cluster of two or three suspended from one point, or a couple hang- 
ing from the body of a third. 
The recently-hatched fish had not all reached the same stage of 
development ; for whilst in some the movements of the body were 
vigorous, and the circulation actively going on, others, lying motion- 
less, would show no circulation of blood whatever. At a further 
stage, as for instance about the 16th or 17th day, at a time when 
the branchial fringes are in formation, all seemed to be alike witli 
respect to the degree of development. 
22nd Aj)ril, 9th day. — State of the circulation immediately after 
extrusion from the egg. (See Fig. 39.) 
The heart (a), consisting of posterior and anterior chambers, lies 
p 2 
