7G RECORD OF CURRENT RESEARCHES RELATINO TO 



cells, to take an excentric direction. The only liglit that its discoverer 

 can throw on its function is the statement that its contents arc 

 watery. 



The shell-gland is next described,* and the heart ; this organ 

 extends from the cephalic region to the sixth thoracic segment, 

 gradually increasing in width as it glasses backwards ; at each end 

 there is an arterial ostium, and in the second, third, and fourth 

 thoracic segments a pair of venous ostia. Invested in an outer layer 

 of connective tissue, the heart of Pallasea canceUus has its muscular 

 layer made uj) of closely-set transversely-striated muscles, each of the 

 fibres of which forms a long spiral coil. The arterial ostia are each 

 provided with a membranous diaphragm, in the centre of which there 

 is a cleft ; the edges of the cleft ajjpear to be provided with a sphincter 

 muscle, and there also seem to be other more delicate circular muscles. 

 There are also lateral muscular membranes which contract at the 

 systole and open the cleft, while at the diastole the fibres of the 

 diaphragm contract and so completely shut off the lumen of the 

 cardiac tubes from the two aortte. The venous ostia are found to 

 have the structure described by Weissmann in Leptodora hyalina, 

 while the observations of Valette St. George and G. v. Sars, which 

 showed that the ostia of the right are directed downwards and back- 

 wards, and of the left side downwards and forwards, are confirmed. 



The series of papers concludes j with an account of the arteries 

 and of the peripheral circulation ; in none of the species examined by 

 the author are there any arteries given off from the sides of the 

 heart. Claus reports that a similar arrangement is to be seen in the 

 Gammarida, but it does not obtain in all the Amphipoda. The 

 presence of an afferent vein, in addition to the narrower artery, in 

 each antenna is noted, and it is pointed out that this arrangement was 

 observed in Cnp-clla by Goodsir in 1842. The structure of the walls 

 of the arteries is described, and it is shown that they are formed by a 

 membrane which is thickened at regular intervals. The course of the 

 circulation in the Crustacea is a matter of importance and of interest, 

 and as the conclusions of the author are somewhat at variance with 

 those of preceding observers, he enters into them in some detail. 

 We must hero content ourselves with stating that the arterial blood 

 from the two great arteries and their branches passes into cm'rents 

 which bathe the various viscera and then pass into the appendages, 

 whence they issue as venous currents, which pass directly into the 

 dorsal venous sinus ; thence the blood passes directly into the heart, 

 without taking any especial course through the gills ; these last 

 structures receive the blood in just the same way as the jointed 

 appendages, and there is, consequently, no distinction in these creatures 

 which can justify us in speaking of distinct arterial and venous 

 streams. In the young Goplana polonica the blood-plasma'Vas of a 

 yellowish red, and in the adult of a more or less greenish colour, and 

 the colour of the blood has a distinct influence on the colour of the 

 animal. The blood-corj)uscles are of a considerable size. Fat drops 

 were to be observed in the blood-plasma. 



* Loc. cit., p. 536. t Loc. cit., p. 564. 



