NOTES ON THE EMBRYOLOGY OF LIHULUS. 
557 
with any structures as yet found in Crustacea or Acerata. It 
has been shown by several students that in the latter group all 
of the appendages are, in the embryo, post-oral both in 
position and in nerve supply. The same is true of the second 
pair in the Crustacea, and in the adult Phyllopods (which are 
admitted by all to be the most primitive of the Crustaceans), 
both anterior pairs receive their nerves from the oesophageal 
commissure, the corresponding (?) ganglia being distinctly post- 
oral in position. 1 It would appear possible that in the very 
early stages of other Crustacea the same condition may exist, 
as in several forms the rudimentary first pair of appendages 
has not a distinctly pre-stomial position. The first to suggest 
itself is Moina, where, according to Grobben (’79), the first 
pair of appendages to appear have a position decidedly posterior 
to the stomodeal invagination. This pair Grobben interprets 
(and possibly correctly) as the second antennae, but there is 
not certainty on this point. In the Nauplius of Palaemon, 
according to Bobretzky 2 (73), the first pair are on a level with 
the labrum, and show distinctly the similarity to the rest of the 
post-oral series. In the corresponding or a little earlier stage 
of Astacus (Reichenbach, ’77, pi. x, fig. 8) they are some distance 
behind the labrum and the oral depression. The same is true 
of Eupagurus (Mayer, ’77, pi. xiii, fig. 18) and of Crangon (my 
own studies). 
The antennae of Insects, on the other hand, always arise 
from the procephalic lobes. The possibility that Peripatus is 
a but slightly modified descendant of the ancestors of the 
Hexapods and Myriapods makes its evidence of some import- 
ance in this connection. Balfour, after a careful study of the 
anatomy, concludes that in Peripatus (’83, p. 217) “the 
antennae are prolongations of the dorso-lateral parts of the 
anterior end of the body and his figures show that the eyes 
intervene between the antennae and the other appendages. 
Kennel, from a study of two other species of the same genus, 
1 Pelseneer’s results as to the brain of Apus [’85] require a modification 
of this statement. 
3 Teste Faxon (’82, pi. xi, fig. 6). 
