ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
467 
they anastomose frequently. The green gland is supplied by the 
antennaries and by the anterior branches of the maxillipedal artery. 
The liver is almost entirely nourished by the superior abdominal artery. 
There are two small valves at the orifices of all the arteries in the heart, 
but the arrangement of the arteries varies somewhat. All the Decapoda 
with the exception of Pagurus are provided with two abdominal arteries, 
an upper and a lower. Important communications put these two vessels 
into connection with one another; these take the form of vascular 
arches which are always more or less symmetrical, and always circum- 
intestinal. The existence of these anastomoses is due to the great 
flattening of the abdomen ; the two vessels having to irrigate parts very 
close to one another, fuse almost at once. The lamellated form of the 
abdomen in the Brachyura destroys completely the symmetry of the two 
abdominal arteries. In the Macrura the upper abdominal artery is very 
much more developed than the lower, in correlation with the great 
development of the dorsal muscles. In the Brachyura the lower artery 
is not as feeble as might be expected. 
All the facts lead us to conclude, with Claus, that the arterial system 
of Decapod Crustaceans is most like that of the Isopoda. 
Renal Organs of Decapod Crustacea.* — rrof. W. F. R. Weldon 
describes the renal organs of certain Candidas ( Pandalus , Virbius, and 
Crangon) in which the structure of the green gland is modified in a very 
remarkable manner. The result of his observations is that these forms 
exhibit a series of modifications which result in the disappearance of the 
whole tubular portion of the green gland, and the hypertrophy and 
specialization of the end-sac. A comparison is made between the 
different parts of the excretory system in the various families of the 
Decapoda ; the general result appears to be that the nephro-peritoneal 
sacs of this division should be regarded rather as enlarged portions of a 
tubular system, such as that found in Mysis and the Thalassinidae, than 
as persistent remnants of a “ coelomic ” body-cavity into which tubular 
nephridia open. 
Female Reproductive Organs of Decapoda. | — Dr. G. Canu has 
studied the structure of the ovaries, oviducts, and cement-glands in 
Decapoda, and has also made observations on the modes of impregnation. 
Beginning with the external morphology of the reproductive organs, he 
notes that they are primitively double and bilaterally symmetrical, that 
in Penaeidse they are least differentiated and nearest the simple type 
exhibited by Nebalia , and that the presence of a vagina and a recepta- 
culum seminis in the females is correlated with the presence of a penis 
in the males. 
In Dromia the receptaculum is formed after copulation as a simple 
evagination of the vagina, which seems to show that the evolution of the 
receptaculum was subsequent to that of the penis. The ovary and 
oviduct are formed from an external stroma of connective tissue and an 
internal stratum of epithelium ; the ovary differs from the oviduct in 
the nature of its epithelium and in the presence of an internal stroma 
arising from the supporting membrane ; the ova are always formed on 
