ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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which have been sent home by Mr. F. J. M. Moir. The largest speci- 
men was 2*2 cm. in diameter, but more commonly the medusae were 
from 1 to 1*8 cm. in diameter. The umbrella is characterized by its 
flattened shape ; the central portion is much thickened, and has the 
form of a nearly hemispherical lens. The velum is sometimes well 
developed, sometimes not so conspicuous. The gastrovascular system 
differs from that of all other Medusae hitherto observed in the relative 
size of its parts ; the mouth and stomach are of so great a diameter — 
two* thirds that of the umbrella — that the lips of the mouth probably never 
completely close the stomach in the adult animal. Mr. G. C. Bourne 
has suggested to the author a possible explanation of this curious 
dilatation of the mouth and stomach. Any increase in the diameter of 
these parts would, obviously, involve a corresponding increase in the 
circumference of the manubrium ; now this last is the bearer of the 
reproductive organs, so that the large size of the mouth would appear to 
be correlated with an enlargement of the area upon which the reproduc- 
tive organs are developed. 
As in Limnocodium , the tentacles are very numerous, and may exceed 
two hundred in number ; in large examples the four primary perradial 
tentacles are hardly larger than the interradial or adradial ; as the 
relative lengths of the tentacles in preserved specimens vary greatly, 
these organs have clearly a considerable power of contraction and 
extension. The lumen of these tentacles is lined by large, thin-walled, 
columnar endoderm cells, which are continuous with the endodermic 
lining of the ring-canal. The thread-cells are small and generally 
arranged in little wart-like groups. 
The sense-organs vary greatly in number in each circle, and are 
arranged at irregular intervals ; they have the form of egg-shaped 
bodies, are refringent, and are attached to one side of a capsule, the walls 
of which are lined by a flattened epithelium. These bodies are com- 
posed of numerous cells, the basal of which are granular or opaque, 
while the apical are quite clear. While they have a remarkably close 
resemblance to the corresponding structures in Limnocodium , they differ 
in structure from all other sense-organs hitherto described in Medusae. 
In Limnocnida, as the author proposes to call this new genus, there is no 
tubular extension of the capsules into the adumbral ectoderm layer of 
the velum as there is in Limnocodium. 
Some specimens have the outer wall of the manubrium quite smooth, 
and these were found to be males and females with the external wall 
covered with ova or spermatozoa in all stages of development. Other 
individuals had small swellings on the manubrium, which were found to 
be stages in bud-formation. 
The author reserves for the present the discussion of the affinities 
and position of Limnocnida tanganjicse , but he points out that if we take 
Haeckel’s system we are beset with almost the same difficulties as 
presented themselves in the case of Limnocodium. 
Porifera. 
Embryology of Sponges.* — Prof. Yves Delage deals at some length 
with this subject. He finds that the progressive differentiation of the 
* Arch. Zool. Expe'r. et Gen., x. (1892) pp. 345-72 (8 pis.). 
2 A 
1893. 
