266 
ZOOLOGICAL LITERATURE. 
We know not if Dr. Muller lias examined the internal struc- 
ture of this air-breathing apparatus; hut a short time since^ 
while dissecting a specimen of Ligia oceanica, in connexion 
with the forthcoming volume of ^^Isopoda^^ in the ^ British Edri- 
ophthalmous Crustacea/ we dissected out what, when placed in 
the field of the microscope, appeared to be a system of tracheal 
tubes or canals, such as are seen in insects. Having made a 
drawing, we intended returning to tlie subjeet at a fresh oppor- 
tunity ; but since then Prof. Westwood, our valued colleague in 
the work, has drawn our attention to the fact that in the genus 
Tylos of the Oniscidai, two or four of the anterior pairs of pleo- 
poda are transformed into air-breathing organs, their interior 
being furnished with canals into which the atmospheric air 
penetrates by means of orifices analogous to the spiracles of 
inseets, for which information we are indebted to Savigny^s 
work on Egypt. 
Considering the agreement that exists between the Ocypodida 
and the Grapsoida in every minute part and organ, except in the 
position of the entrance to the air-breathing chamber. Dr. 
Miiller thinks that the sehools will scarcely have an answer to 
this faet, and must place themselves on the old theological 
standpoint, so highly decried among us ” (the followers of Dar- 
win), from which the occurrence of any arrangement is con- 
sidered explained when one can prove its conformability to the 
need of the animal possessing it. 
VI. Dr. Muller then points out the variation in form and 
position of the heart in the Edriophthalmous Crustacea, which 
in the Amphipoda is in the pereion, and in the Isopoda (except 
in TanaiSj where it is as in the Amphipoda), in the pleon, and 
draws conclusions from it favourable to the doctrine of Darwin. 
VII. He then enters into the development of the Decapod 
Crustacea, and gives a full account of that of the genus Peruaus, 
from the Nauplius form to that of the perfect animal, of 
which the character is shown in his paper on the development 
of the Prawns, at page 281. Speaking of the development of 
PalinuruSy he tells us of the circumstance of Prof. Claus having 
taken from the ovum an embryo with a perfeetly formed body, 
having the appendages of the pleon and of the two posterior 
somites of the pereion wanting ; that it had a single eye, toge- 
ther with a pair of closely-set eyes ; that the first pair of an- 
tennae were simple, and the second provided with a secondary 
branch, and that the succeeding appendages were long and 
equally branched. And he appears to liesitate in accepting the 
observation of Coste, who obtained larvae resembling Phyllo- 
soma out of the eggs of this same crustacean. Dr. Muller does 
not appear to be aware that this same form of larva was first 
taken from the egg of Palinurus as far back as 1857 by the late 
R. (I. Couch, which M. Coste’s observation tended to verify ; 
