MUSEUM OF COMPARATIVE ZOOLOGY. 325 
volume of the Annals of Natural History.* In this communication the 
author gives a brief description and rude figures of four larval stages of 
the ditch prawn, Palemon variabilis [Palemonetes varians Heller 1]. 
The earliest form represented is that which the larva assumes immedi- 
ately after exclusion from the egg. The first pair of antenne are por- 
trayed with two terminal, one-segmented branches, a condition not seen 
in any other figures of the first larval stage of Palemon. As in Thomp- 
son’s figure of the same stage, only two pairs of swimming-feet are rep- 
resented. Behind them are the rudiments of the true legs in the shape 
of three pairs of small, simple, two-jointed processes. The number of 
abdominal segments is plainly exaggerated. 
In the second stage, “ascertained by observing the moult of the former," 
the carapace is armed with a dorsal spine at the base of the rostrum, and 
all the thoracic legs are present! The posterior pair are destitute of the 
natatory branches ; the chel; are developed. It is noteworthy that the 
author expressly states that the abdominal appendages have begun to 
appear, excepting the last pair. If this be correct, it is certainly an excep- 
tional order of development among the Macroura. Commonly in this group 
the posterior pair appear before the other abdominal appendages. 
In the third stage, ‘also ascertained by witnessing the moult,” the 
carapace has two dorsal and supra-orbital spines, and the posterior pair 
of abdominal limbs have appeared. 
The fourth stage was not obtained directly from the third by observ- 
ing the moult. The larva now has three dorsal spines, and, excepting 
the want of external branches to the last pair of thoracic legs, agrees 
well with Thompson’s third stage. The next moult brought it to the 
condition of the adult prawn. 
It is obvious from the above account that the number of forms passed 
through by the larva before reaching the adult shape is much smaller 
than in the case of Palemonetes vulgaris, unless there is error in the 
observations of DuCane. 
The next observation bearing upon the development of Palemon is 
found in Fritz Müller's * Für Darwin.” t It consists of a brief description, 
accompanied by a wood-cut, of what seems to be the first larval stage. 
The researches of Bobretzky upon the development of Palæmon, pub- 
lished in the Russian language, at Kief, in 1873, have already been 
* Letter from Captain DuCane, R. N., . . . on the subject of the Metamor- 
phosis of Crustacea, Ann. Nat. Hist., Vol. Il. pp. 178 - 181, Pl. VI, VIT. 1839. 
+ Für Darwin. 1864. English Trans. by W. S. Dallas, p. 55, Fig. 27. ۰ 
t Zapiski Kiefs. Obshtshest. Yestestvoispitatalyei, Vol. III. pp. 186-252, Pl. IV- 
VI. 1873. Hofmann und Sehwalbe's ** Jahresberichte,” Vol. II. pp. 817,818. 1875. 
