18 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Correlated with the development of sperm in the gonad is the very 
great enlargement of the penis, first and second penial glands, and the 
vagina, the two latter becoming greatly distended by secretion; while 
correlated with the development of the egg follicles, which takes place 
mostly after the parts mentioned above have begun to resume their 
normal size, is the very considerable enlargement of the two glands 
opening into the hermaphroditic duct and the partial contraction of the 
gonadial cavity which, ho wester, still contains some sperm even after 
the eggs have reached a late stage in their development. 
Perhaps the most interesting question in connection with this animal 
is as to whether we are dealing with a paedogenetic condition of the 
young of some other pteropod or whether this is a sexually adult form 
in which some larval characteristics have been retained. Fol ('75) 
has described an egg-producing form, 2 to 2.5 mm. long ("Clio auran- 
tiaca"), from Messina which Pelseneer ('88) regards as the paedo- 
genetic young of Clione flavescens though Fol states that he kept the 
animals in perfect health for three weeks without any alteration in the 
ciliated bands. It is likewise possible in the case of our Paedoclione 
that we have an instance of paedogenesis, but even if this be the case, 
the animal cannot be regarded as the young of any known pteropod. 
Its larval characters are only the three bands of cilia, its small size, 
the possession of a distinct caudal lobe, and, possibly, the small number 
of radular teeth. The many points of structure in which it differs 
from all allied forms cannot be explained on grounds of immaturity, 
and hence it has seemed best to describe the animal as new, leaving 
to the future the decision of the question whether or no it be actually 
the adult or, if paedogenetic, the discovery of the adult form. 
