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SUMMARY OF CURRENT RESEARCHES RELATING TO 
present in the stages described by him. The epithelium of the left 
epicardial cavity is continued into the vessels of the test, and presents 
the characters of the stolon of the compound and social Ascidians, except 
that it does not produce buds. The relation of the epicardium of Ciona 
to that of Clavelina shows, in the author’s opinion, that the latter is a 
more highly specialised type than the former, and that the epicardial 
organ consists primitively of two parts : — (1) a respiratory cavity in 
•communication with the branchial sac, and (2) a stolon. In Ciona both 
regions are present ; but in social and compound Ascidians the latter is 
greatly developed at the expense of the former. 
INVERTEBRATA. 
Mollusca. 
Excretion in Mollusca.* — Prof. L. Cuenot publishes a comprehensive 
memoir on this subject based on researches made at Nancy and Roscoff. 
We can summarise here only the more general of his conclusions. In 
Mollusca generally there are three sets of excretory organs. Firstly, the 
nepbridia, which eliminate indigo aud whose cells have usually tyi acid 
reaction. When two nephridia are present they may, as in Patella, be 
physiologically similar, or may be differentiated as in Trochus and Hali- 
otis , where the right excretes indigo and the left carminate of ammonia. 
Where one nepliridium only is present, it often contains two kinds of 
cells, those which are ciliated and excrete carminate of ammonia and 
the non-ciliated which excrete indigo. Secondly, in Amphineura, Denta- 
lium , and Gastropoda, there are scattered cells in the connective tissue 
which are excretory in function, and correspond to the pericardial glauds 
of Lamellibranchs and the branchial hearts of Cephalopoda. All these 
cells have an acid reaction and excrete carminate of ammonia and 
tournesol. Thirdly, in certain Gastropods the liver contains excretory 
cells which shed their products into the intestine. The Lamellibranchs 
furnish an admirable example of a mode of excretion common in Inver- 
tebrates, where excretory cells secrete waste products which are subse- 
quently taken up by the phagocytes of the blood and carried to special 
regions of the body. This “ bastard ” process of excretion the author 
regards as a striking example of the imperfect functioning of organs, the 
storing-up of the waste products within the body being highly disadvan- 
tageous to the individual and destructive of the necessary co-ordination 
of parts. 
The methods employed were by physiological injections of colouring 
matters ; and the paper includes a discussion of the value of the method, 
illustrated by comparative tables. 
y. Gastropoda. 
Molluscs of Great African Lakes. t — Mr. J. E. S. Moore, in his third 
paper on this subject, deals with Tanganyikia rufojilosa, Spekia zonata , 
and in a fourth paper with Nassopsis and Bytkoceras , all from Tan- 
ganyika. All the evidence, he says, which has been afforded concerning 
the nature of these halolimnic Gastropods points to their vast antiquity. 
* Arch. Biol., xvi. (1899) pp. 49-96 (2 pis.). 
f Quart. Journ. Micr. Sci., xlii. (1899) pp. 155-85 (6 pis.), 187-201 (2 pis.). 
