44 MANUAL OF THE MOLLUSCA. 
hatched, and they enter life under the same form,—that which 
has been already referred to as permanently characteristic of 
the pteropoda. (Fig. 69.) 
The Pulmonifera and Cepha’cpoda produce large eggs, con- 
taining sufficient nutriment to support the embryo until it has 
attaimed considerable size and development ; thus, the newly- 
born cuttle-fish has a shell half an inch 
long, consisting of several layers, and the 
bulimus ovatus has a shell an inch in 
length when hatched. (Fig. 31.) These 
are said to undergo no transformation, 
because their laryal stage is concealed in 
the ege. 
The researches of John Hunter+ into 
the embryonic condition of animals, led 
him to the conclusion that each stage in 
the development of the highest animals 
corresponded to the permanent form of 
some one of the inferior orders. This 
grand generalisation has since been more exactly defined and 
established by a larger induction of facts, some of which we 
have already described, and may now be stated thus :— 
In the earliest period of existence all animals display one 
uniform condition; but after the first appearance of special 
development, uniformity is only met with amongst the mem- 
bers of the same primary division, and with each succeeding 
step itis more and more restricted. From that first step, the 
members of each primary group assume forms and pass through 
phases which have no parallels, except in the division to which 
each belongs. The mammal exhibits no likeness, at any period, 
to the adult mollusc, the insect, or the star-fish; but only to 
the ovarian stage of the invertebrata, and to more advanced 
stages of the classes formed upon its own type. And so also 
with the highest organised mollusca; after their first stage they 
Fig. 31.* 
Jabial tentacles; s s’, the stomach; 0, branchie; A, heart; v, vent; 7, liver; 7, renal 
organ ; a, anterior adductor; a’, posterior adductor ; 7, foot. The arrows indicate the 
incurrent and excurrent openings; between which the margins of the mantle are 
united in the fry. 
* Egg and young of bulimus ovatus, Miill. sp., Brazil, from specimens in the collec- 
tion of Hugh Cuming, Esq. 
+ “In his printed works the finest elements of system secm evermore to flit beYore 
him, twice or thrice only to have been seized, and after a momentary detention to 
have been again suffered to escape. At length, in the astonishing preparations for his 
museum, he constructed it, for the scientific apprehension, out of the unspolicn 
wpbabet of natnre.”—Coleridge. 
