Miscellaneous. 271 
is of greater depth, and has a small circular opening. This is what 
M. Pouchet calls the old mode of building; ind: M. Noulet deduced 
that it is still followed by the h ouse-martins of his district. His 
opinion is that iL perso 8 dil spi dispu y M. e is 
nfir a 
model which is peculiar » d which n chang 
petuated from age to age."— Comptes Rendus, 7 uly 4, P5870, aa 7 79.81. 
On the Scissiparous vg Niece of the Naidina. 
By M. E. Pzzn 
The investigations upon the scissiparity e the Naides and allied 
opem at present relate only to Nats proboscidea. Gruithuisen, 
F. Mi 
aides distin en two modes of agamic genera- 
Gea: one individual divides at first into two others of equal length; 
then each of the individuals thus formed produces a new one at its 
der by a process of gemmation. 
The observations that we have made upon Dero obtusa enable us to 
present the mode of reproduction of the Naides under another aspect. 
st in Nais proboscidea chains of three or four individuals are 
frequently met with, in Dero obtusa we have never seen more than 
two individuals placed end to end. The head of the hinder indivi- 
dual and the tail of the anterior one are formed, neer mon 
as indicated by Max Schultze in his Wais. These two individuals 
separate before we observe in them any trace of fresh ratini 
but in front of the respiratory lobe which terminates the body we 
always see, so long as the indiviđual is not adult, numerous animals 
in course of formation, and in which we may follow the develop- 
ment of the setigerous saes, the segmental organs, the muscles, 
When the two separated individuals have attained a sufficient length, 
the median scissiparity recommences in them, as in the single indi- 
vidual at the cost of which they were formed. 
Now, as this s phenomenon is only produced when the animal has 
attained a certain length, it follows that the hinder individual of 
the second generation will be formed of segments which were not 
developed until after the separation of the individual, but formed 
an integral part of that individual when they were produced. 
Thus the Dero first enlarges by the formation of ca in front 
of its vibratile Ed and then undergoes scissiparous 
nating after the individualization of the two primary Deros, as we 
have explained, 
