ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
449 
In addition to its dermal skeleton Limulus lias three other kinds of 
skeletal structures of very obvious significance; (1) cartilaginous gill- 
bars, which are histologically very much like the cartilage of Petromyzon ; 
(2) segmeutally arranged cartilages partially surrounding the ventral 
cord ; and (3) the cartilaginous cranium. This last is not a simple 
plate, as described by Lankester and others, but “ the whole forms a 
perfect picture of a simple cartilaginous cranium such as we might 
expect to find in some primitive Vertebrate.” 
The author urges that we can only fail to regard these facts as proof 
positive of genetic relationship at the cost of destroying the very founda- 
tions of the science of Morphology. 
e. Crustacea. 
Physiology of Decapod Crustacea.* — M. L. Cuenot has published 
an extended memoir detailing the results which we have already! noted. 
New paragraphs deal with the presence in the connective tissue of cells 
containing albuminoid spheres ; these may be considered as elements of 
reserve, for their contents disappear completely after a prolonged fast. 
In Galathea and Palinurus fat-cells were sometimes observed. 
In the Brachyura the integument, on each side of the pericardium, is 
provided with a pouch formed by connective tissue, which is traversed 
by strong muscular bundles ; these pouches, the function of which is 
unknown, are found in a rudimentary condition in the Anomura and the 
Palinurkke. 
The amoebocytes of the blood represent the different stages in the 
development of one and the same element ; the young (hyaline cells) 
gradually form eosinophilous grains ; when the eosinophilous or mature 
cell degenerates the grains appear to be dissolved in the blood. The 
degenerate cells are swallowed by the young, and so disappear from the 
circulation. The lymphatic gland which produces the hyaline cells 
invests the dorsal surface of the masticatory stomach. 
There is only one type of phagocytes in Decapods ; this is seen in 
the young stages of amoebocytes; they have either a neutral ( Astacus ) 
or acid reaction, and are capable of slowly digesting albuminoids. 
These phagocytes are attracted by solid injected particles, degenerate or 
diseased organs, or dead parasites ; they free the organism from them, 
either by enclosing them in a sort of isolating cyst or by digesting 
them, but they are always inactive towards living parasites of every 
kind ; this peculiarity is, no doubt, related to the presence of a chitinous 
carapace. 
Median Eye of Adult Crustacea.! — Dr. H. C. Bumpus has a pre- 
liminary note stating that he has been able to trace the median eye, so 
generally present in larvae and lower Crustacea, through several Bra- 
chyura, Macrura, Schizopoda and Stomatopoda, and in no case has he 
found the organ absent. In some, but not all cases it is easily seen 
from the exterior. Further details are promised. 
Correlation of certain External Parts of Palsemon serratus.§ — 
Mr. H. Thompson, following the methods of Prof. Weldon, has deter- 
* Arch, de Biol. xiii. (1894) pp. 245-303 (3 pis.). + See ante, p. 194. 
t Zool Anzei^r., xvii. (1894) pp. 176 and 7. 
§ Proc. Boy. Soc. Lond., lv. (1894) pp. 234-40. 
