DEVELOPMENTAL HISTORY OF THE MOLLUSCA. 
39 
most useful instrument brought gently down so as to touch the upper pole of the egg. 
The adhesion of the delicate egg to the glass was now sufficient to maintain it in the 
erect position. The eggs were examined thus in the living condition, and, in some 
cases, after the addition of dilute acetic acid. The method of hardening and cutting- 
sections was not applied by me to the study of the deposited eggs* of Loligo , which, on 
account of their great transparency, offer every facility for study in the fresh state with 
even the highest powers* ; but the growth of the ovarian egg and its envelopes or 
prseseminary development f has been followed by means of sections stained with car- 
mine, cut from eggs hardened in absolute alcohol, and some in chromic acid, in the 
usual way. 
The Ovarian Ovum. 
The ovary of Sepia and of Loligo at the breeding-time is an arborescent organ, 
formed by a series of branches and twigs, on the ends of which the eggs are seen like 
so many grapes on a bunch, but differing from a grape-bunch in the fact that the eggs 
are of very various sizes (Plate 11. fig. 13). I do not propose here to go into the larger 
anatomical features of the ovary, but to confine myself to the history of the growth of 
the individual eggs as exhibited in the variously sized specimens which occur in one 
and the same adult ovary. This, accordingly, excludes all question of the earlier 
development of the ovary and the ultimate origin of its constituent cells, a matter which 
must be treated of in due course in connexion with the later embryonic history of the 
developing Cephalopod. 
Limits of size of the Ovarian Egg in Sepia. — The observations which follow, unless 
the contrary is stated, must be understood as relating to Sepia. The preparations to 
which they refer, some of which are represented in Plates 11, 12, were made in the 
histological laboratory of Exeter College during the present year (1873). The ovarian 
eggs of both Loligo and Sepia were also made the subject of study by me at Naples 
in the spring of 1872, when they were in the fresh condition. 
The smallest eggs in the mature ovary of Sepia or of Loligo are to be found sessile 
among the long peduncles or stalks which support riper eggs. The smallest observed 
in Sepia were about -g-jjo of an inch in diameter. Before quitting the ovary the 
egg attains to nearly a quarter of an inch in long diameter, and has more than a 
hundred thousand times the bulk of these smallest egg-cells. The acquisition of new 
material by the egg-corpuscle, in passing from this smaller to that larger condition, is 
accompanied by structural arrangements, which are illustrated in Plates 11, 12. 
First Stage of Ovarian Growth. — In Plate 11. fig. 14, the egg-corpuscle, with its nucleus 
and nucleolus, surrounded by a moderately developed “ body ” (the best, since the most 
indifferent, term which can be applied to that part of a nucleated plastid which is some- 
* In the spring of 1874 I studied the development by means of hardening and cutting sections. 
t Prsesemin ary = before the junction of the semen with the ovum. Postseminary = after the junction of the 
semen with the ovum. Insemination = the junction of semen with ovum. 
