445 
GENESIS, OE PARTHENOGENESIS ? 
8. The egg presents the same essential composition as that of all other 
animals. The zoosperms are filiform, motionless, and develop them- 
selves from the granular contents of the spermatic cellule. 
9. After fecundation the eggs axe extruded, and undergo the usual 
embryonic changes. 
Tlie other division of Protozoa (sponges), which, like the 
infusoria, also multiply by gemmation and fission, was disco- 
vered by Lieberkuhn to possess the male and female elements 
characteristic of sexual distinction, and to produce ova, which 
were first transformed into nonciliated embryos. The meta- 
morphoses of both divisions of Protozoa prove to be remark- 
ably complex ; but the point we are desirous of emphasizing is 
the undoubted occurrence of a true generative act apart from 
all phenomena of metamorphosis. It is also worthy of notice 
that the production of a multiple progeny from the single 
nucleus and nucleolus by endogenous division has thus become 
a settled fact. After such clear demonstration in this the 
lowest class of animals, it is unnecessary to repeat the obser- 
vations which prove the same thing for all the higher animals. 
The formula of our illustrious Harvey — “ omne vivum ex ovo” 
— is established as the widest possible generalization, including 
every form of animal life — 
Et nunc bistoria quod ratio ante fuit. — Ovid. 
We return to the phenomenon of Aphis larvation. Is it the 
consequence of a generative process, or an instance of internal 
gemmation ? and is the distinction between oviparous and 
gemmiparous reproduction an essential one ? 
The former question is one of observation ; the answer to 
the latter turns upon the definition of an egg and a germ ! 
According to ordinary notions, an egg is the product of a 
true generative process by sexually distinct organs, and this 
product must be endowed at least with the capacity of fecunda- 
tion. A germ is a “ living thing,” and capable of development 
and independent existence; but neither its composition nor 
structure is that of the egg ; nor is immediate fertilization 
a condition of its growth. Holding to these definitions, we 
must accordingly distinguish between all “ living things ” 
derived by gemmation and the living product of a fertilized 
egg. And, accepting “ Parthenogenesis ” as the doctrine of a 
special form of development from an unfertilized egg, we must 
distinguish between this mode of reproduction and that which 
consists in the successive partition of an individual commonly 
known as “ alternate generation,” but which is not generation 
at all. cc Alternate generation” belongs to the same class of 
phenomena as gemmiparous reproduction. 
We therefore agree with Leuckart that a true generative 
