234 ■ EEPORT— 1880. 



affecting the muscular wall of the heart, and travelling from behind 

 forwards, thus demonstrating that this condensed heart is a true dorsal 

 vessel. On the stimulus of the entrance of renovated blood, it is only the 

 hinder half or two-thirds of the heart that contracts immediately. This 

 forces the blood into the anterior half, which contracts while the posterior 

 division is dilating. When the temperature is increased, as a general rule 

 the diastolic phase is abbreviated, the number of pulsations rising at the 

 same time. M. Plateau has also succeeded in making experiments on the 

 action of the cardiac nerve of Lemoine, an unpaired branch of the stomato- 

 gastric ganglion. It is shown that excitation of this nerve quickens the 

 pulsations of the heart and augments their energy, while the division of 

 it lessens the heart's action. Whereas excitation of the pereionic ganglia 

 always retards the heart's movements, being the converse of a similar treat- 

 ment of the cai'diac nerve. 



M. Plateau likewise says that acetic acid applied to the heart-substance 

 arouses its contractions even after they have ceased, and maintains them 

 for several hours. • 



M. Jobert, in the ' Annales des Sciences Naturelles,' 6th ser. vol. 4, has 

 drawn attention to the character of respiration in the terrestrial Crustacea of 

 the decapod order. He says that in an examination of the anatomy of these 

 animals we iind that they are provided with branchia the same as other 

 crabs both marine and fluviatile, and their habit of life in relation to 

 these organs, which are essentially constructed for aquatic respiration, 

 appears to be paradoxical, and has not escaped the attention of naturalists. 

 In 1825 Geoffrey Saint-Hilaire suggested that the ridges which line the 

 respiratory cavity of Birgus latro assisted the respiration — an hypothesis 

 that in 1828 was combated by MM. Milne-Edwards and Andouin, who 

 studied the respiratory cavity of the Gecarcinida;, and attributed to a fold 

 in the membrane which lined the internal cavity, the power of storing up 

 a supply of water, with which it regularly laved the branchial apparatus, 

 this water not serving respiration directly, but by its slow evaporation 

 saturating with moisture the air which is brought into contact with the 

 branchia, and so precluding the dessication of these organs. 



M. Jobert has endeavoured to verify the correctness of these two 

 opinions, and for this purpose has studied the habit of living specimens 

 of Uca, Gelassimus, Cardisoma, Orapsus, Telphusa, and Tylocarcinns. 



He takes as typical, Uca ttjiar, in which the respiratory apparatus is the 

 most complete, and points out the vai-ious modifications which he has 

 noticed among the other Crustacea. 



The branchial chamber is lined with a soft blackish grey membrane 

 in continuity with the vertical septum {cloison^. In a histological study of 

 this membrane we find the elements of tihe hypodermic membrane of Crus- 

 tacea, for instance, large pigmentary cellules, special hypodermic cellules, 

 and some peculiar fibres, either solitary or nnited in bundles in the form of 

 X, which exist all over the membrane. This membrane is lined or covered 

 by another very thin membrane capable of being separated from it by the 

 aid of maceration in a very weak solution of acetic acid, and it appears 

 to be a thin surface of chitin. 



M. Jobert opened more than 200 specimens after having been confined 

 for two, four, and six days in a perfectly dry place, and never found a drop 

 of water, or ever found the surface of the branchia moist ; the cavity was 



> Nature, 1879, xix. 470. 



