60 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The lateral mode of locomotion of tlio Brachyura affords 

 aiiparcntly au excellent opportunity for making experiments on 

 traction, but in practice it is not found to be so ; crabs appear to 

 draw very badly, but it is possible that, on account of their fear, 

 they do not exert themselves to the utmost ; sometimes the animal 

 does not use all its legs, or the different joints of one and the same 

 leg do not move in the same plane, and the surface of the section of a 

 muscle is so small that gross errors may easily intervene. The 

 absolute force of the motor muscles of the joints of the legs may, how- 

 ever, be regarded as analogous to those of the mobile joints of the 

 forceps. 



Anatomy of the Spider Crab.* — E. A. Andrews describes in 

 great detail the anatomy of the spider crab (Libinia emargincUa 

 Leach), illustrating the paper with 20 figures. 



Circulation of Schizopoda and Decapoda.f— The disposition of 

 the heart and the vascular system in general of the Schizopoda has 

 been studied by C. Glaus in several species of Mi/sis and in the 

 genera Siriella, Mysidopsis, Lejptomysis and Pseudosiriella ; in Siriella 

 the heart extends through the whole thorax, and may be recognized 

 therefore as a more archaic type, similar to the Phyllopod heart ; in 

 Mysis the heart is considerably shorter, but the absence of an internal 

 muscular network is a primitive character. In Mysidoiisis the heart 

 is still more curtailed and possesses only two pairs of ostia, which are 

 so close together that they have been regarded by previous 

 investigators as forming but a single pair. From the anterior end of 

 the heart arise two lateral and a median aorta ; from the lower surface 

 of the heart arise two vessels, which supply the alimentary canal and 

 its dependent glands, and the sexual glands ; in the hinder region of the 

 heart arises the " descending aorta," which communicates with the 

 sternal artery ; finally from the hinder extremity of the heart arise 

 two rudimentary lateral trunks and the abdominal aorta. 



The anterior median vessel, guarded at its exit from the heart by 

 two valves, sui)plies the anterior region of the head, including the 

 brain, eyes, and anterior antenna) ; the vessels supplying the eyes 

 divide up into au extraordinarily developed capillary plexus in the 

 eye stalk. 



The vessels which spring from the lower surface of the heart corre- 

 spond to the single hepatic artery of the higher Decapoda, and in being 

 three in number resemble the conditions observable in the Hyperid^. 

 In the Euphausidixi, on the other hand, there is only a single hepatic 

 artery as in the higher Decapoda. The abdominal aorta, as in the 

 Decapoda, runs along the upper side of the gut as far as the telson. 



The fine capillary branches of the arterial trunk open freely into 

 the body-cavity, and only form plexuses in the nerve-centres ; the blood 

 from these plexuses is returned into arterial vessels which themselves 

 open into the body-cavity. There are no venous trunks, only in- 

 completely defined spaces in the body-cavity, which occasionally (in 



* Trans. Connecticut Acad. Arts and Sci., vi. (1884) pp. 99-121 (3 pla.). 

 t Arbeit. Zool. Inst. Univ. Wien, v. (1884J pp. 271-319 (9 pis.). 



