948 SUMMARY OF CURRENT RESEARCHES RELATING TO 



find expression ou tbo one hand in opposed cLanges of form, and on tho 

 other in contrary electromotor activities." " The mutual relation of tho 

 two processes simultaneously set up in the muscle, may have a different 

 import in relation to tho mechanical effect of stimulation, from that 

 exhibited in relation to the electromotor activities." The author points 

 out that Fano's experiments ou the cardiac muscle of the tortoise also 

 showed an imjKrfect agreement between tho changes of form and tho 

 simultaneous electric phenomena. Finally, it is to be noted, as Gaskell's 

 researches have shown, that in several respects there are analogies 

 between the innervation conditions of the cardiac muscle of Vertebrates 

 and those of the claw muscles of crabs, as especially exhibited in tho 

 galvanic consequences of stimulation. 



' Challenger ' Crustacea Macrura.* — Mr. C. Spcnce Bate has com- 

 pleted his investigations into the 2000 specimens of macrurous Crustacea 

 which were collected during the voyage of II.M.S. ' Challenger.' In 

 ttdilition to the detailed descriptions of this vast quantity of material, the 

 author gives an interesting introduction in which he treats of the 

 morphology of the group. With slight modifications, the classification 

 proposed in 1883 by Prof. Huxley is accepted, the group being divided 

 into the Trichobranchiata, Dendrobranchiata (= Penseidea, Dana), 

 Phyllobrauchiata, and Ammobranchiata. 



Structure of Asellus.f — Herr B. Eosenstadt has investigated the 

 structure of Asellus aquaticus and related Isopods, and notes the points 

 in which his results differ from those of Sars. 



(1) Vascular system. The heart begins at the boundary of the fourth 

 and fifth segment, and extends into the reduced abdominal segments. 

 The two pairs of venous ostia are symmetrically disposed. The aorta 

 becomes smaller till it reaches the cardiac portion of the fore-gut, where 

 it expands into a vesicular enlargement, and gives off two ophthalmics, 

 a peri-cesophageal ring, and branches to antennae and brain. From tho 

 heart there also rise two lateral arteries, three pairs of thoracics, and a 

 fourth i)air to the reduced abdomen. The peri-oesophageal ring is 

 continued into a ventral artery, connected by seven pairs of vessels with 

 the thoracics. There are no branchio-pericardial vessels. On the dorsal 

 surface of the heart of Asellus embryos are two delicate strands, also 

 seen in Idotea and Jacra, and regarded by Claus as sympathetic nerves. 

 The peculiarities of Jaera are discussed. 



(2) Tlie Nervous system of Asellus and other Isopods is then de- 

 scribed, but the results are chiefly corroboratory of Brandt and other 

 previous investigators. (3) In regard to the alimentary system, two 

 pear-shaped glandular sacs on tho posterior end of the upper lip of 

 Asellus, and similar glands are described. The structure of the gut is 

 briefly discussed. In the mid-gut gland only epithelial cells of different 

 sizes were to bo seen. Weber's hepatic cells and ferment-cells are large 

 and small stages of the same kind of cells. 



(4) Excretory system. At the base of the outer antenna? lies a rudi- 

 mentary antennary gland. Coiled canals by the side of the stomach 

 contained urates, and were seen to open by a duct on the base of the 

 second maxillas. This gland, seen in six genera, seems to be really a 

 shell-gland, such as Claus has observed in Apseudes. (5) Beproductive 



* ' Challengtr' Reports, Hi. (1888) xc. and 942 pp. (157 pis.)- 

 t Biol. Ceutialbl., viii. (1888) pp. 452-62. 



