322 
ZOOLOGICAL LITLllATURE. 
terminates in a simple telson instead of, as in Phyllosoma, being 
supported by a pair of well-developed pleopoda, and that it car- 
ries, besides the gnathopoda, but three pairs of pereiopoda, instead 
of five as seen in Phyllosoma. But he says they exhibit those 
general characters which belong to that genus — for instance, 
the absence of branchm, and the flattened ^ membranous, dia- 
phanous body, that is divided into two bucklers, the larger of 
which constitutes tbe cephalon and supports two pairs of an- 
tennae and a pair of pedunculated eyes, Avhilst the less forms the 
pereion bearing the gnathopoda and pereiopoda, which support 
secondary ciliated appendages. 
As our experience has induced us to believe that the flattened 
appearance of the animal is due to the plan of observation — 
that is, whether the anipaal be examined from a dorso-ventral or 
lateral point of view — so our observation has convinced us that 
the small vesicular appendages attached to the coxae of the pe- 
reiopoda are true branchiae, of which there are two pairs to each 
except the last, and are not, as suggested by Prof. Milne- 
Edwards, the vestiges of the fouet * or external branch of 
these appendages. ButM. Gerbe remarks that between the ear- 
liest form of the larva of a crustacean and that of the latest there 
are progressive changes, and these he has observed sufficiently to 
justify him in regarding the larva of Palinurus as an earlier 
stage of Phyllosomay and tliat the latter is only the layva of 
Palinurus which has undergone several moultings, and therefore 
represents the young of Palinurus in a more advanced state of 
development, but that he is still engaged on researches which he 
hopes will bear him out in these conclusioiis. If they should, it is 
remarkable that the abundant larvae of so common an animal on 
our coast should be so rarely found ; for we know of but one or 
two specimens of Phyllosoma that have been taken ; and those 
are generally supposed to have drifted from warmer latitudes, 
where they exist in large numbers as well as of comparatively a 
larger size. On the other hand, it may be remarked that a 
young Palinurus or a young Homa7'us is a thing unknown. The 
smallest Lobster that we have seen is five inches long, and we 
have never seen a Palinurus so young except in the earliest 
larval stage. It is therefore a mystery yet to be unravelled, 
in what form and where they exist from the time that they quit 
the ovum in a larval condition until we meet with them in thq 
youngest known matured form. 
As'McIDtE. 
Dr. Alex. Braj^dI? communicated to the Imperial Academy 
of St. Petersbui'g the results of his physiological experiments bn 
the heart of the freshwater Astdeus (Bull, de P Academic Im- 
* Hist. «1os Omst. t. iL p. 474. 
