lv ; 
and from the pupa to the imago on the other, are more gradual 
than most entomologists would have been inclined to suppose. 
There is, he concludes, “no pause in. the metamorphosis for a 
special biological design, such as obtains in the Lepidoptera and 
majority of the lower insects. The terms larva, pupa and imago 
are not therefore absolute terms.” I need hardly say that even 
to the Lepidoptera the same observations might, in my opinion, be 
applied. 
Mr. Packard is perfectly satisfied that Audouin, Latreille and 
Newman were correct in believing that the terminal portion of the 
so-called thorax in Hymenoptera is in reality abdominal. During 
this stage, he says, “the basal ring of the abdomen is plainly seen 
to be transferred from the abdomen to the thorax.” 
M. Balbiani, already so well known for his researches among the 
Infusoria, has communicated to the ‘Comptes Rendus’ a very 
remarkable memoir on the generation of the Aphis. If we consider 
that almost every one who has studied the anatomy of the Inverte- 
brata must have had his attention particularly directed to the very 
interesting phenomena presented by the agamic reproduction pre- 
valent in this family, and if we remember the numerous memoirs on 
the subject by Bonnet, Réaumur, Degeer, Kyber, Duvau, Morren, 
Steenstrup, Leydig, Leuckart, Owen, Huxley, and many others, we 
might well have thought that this problem if any in Natural History 
had been thoroughly exhausted. 
Nevertheless, in opposition to the now almost unanimous opinion 
that the production of young by the viviparous females is a case of 
parthenogenesis, M. Balbiani comes forward and asserts that the 
viviparous specimens are hermaphrodites after all. 
| As regards the first stages in the formation of the egg, up to the 
appearance of the blastoderm, he agrees in the main with other 
observers. 
Commencing with the viviparous individuals, he has satisfied him- 
self that the whole inner surface of the blastoderm is lined with a 
delicate membrane, which extends like an envelope round the central 
vitelline mass. ‘This membrane, with a portion of its contents, 
bursts through the posterior part of the blastoderm, and protrudes 
in the form of a hernia. This portion by degrees detaches itself 
from that remaining in the vitelline vesicle, and engrafts itself to the 
epithelial cells lining the ovarian chamber. ‘The vitelline vesicle 
