ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 807 



the result of whicli he finds that the leech secretes from its mouth a 

 fluid which destroys the blood ferment without producing any other 

 observable change in the blood. This fluid injected into an animal 

 produces but slight constitutional disturbance, and is eliminated by 

 the kidneys. The action on the rabbit is the same as on the dog ; 

 on crustacean blood it is inert. It has no action on the curdling of 

 milk. It slightly hastens the clotting of myosin, and hastens rigor 

 mortis. 



*- - Org-anization of Echinorhjmchi.* — A. Safftigen recommends that 

 Eclnnorlqincld be killed slowly by being placed in a O'l per cent, 

 solution of osmic acid, when they die in an expanded condition. 

 Osmic acid is also the best reagent for histological investigations 

 generally, but chromic acid and borax carmine are the best for a 

 study of the nervous system. 



The subcuticula is described as being composed of a complex 

 plexus of fibres, a granular ground substance being altogether absent. 

 The muscular character of these fibres is one which their general 

 arrangement would lead us to accept. The author thinks, with various 

 preceding writers, that the lemnisci are direct continuations of the 

 subcuticula of the neck. 



The true muscular tissue serves as the material from which most 

 of the organs are built up ; when extended, it is seen to form a con- 

 tinuous layer interrupted only by small spaces, and, as a rule, 

 containing a large number of nuclei ; indeed the structure appears to 

 be syncytial. This tissue presents many points of resemblance to 

 that of Nematodes, for, as in them, it consists of a fibrillated differ- 

 entiated contractile substance, of a medullary layer, which is formed 

 of a plexiform protoplasm, in the spaces in which there is a muscular 

 fluid, and which contains nuclei, and of a structureless refi'acting 

 membrane, which corresponds to Schneider's sarcolemma. 



After a full discussion of the muscular system, the nervous system 

 is dealt with ; the cells of the cerebral ganglia are said to be pro- 

 portionately larger, and, with the exception of the ovarian and seminal 

 elements, are almost the only cells in the body which have a distinct 

 peripheral contour. The central portion of the ganglion is occupied 

 by a plexiform jn'otoplasm with numerous vacuoles and some nuclei ; 

 the peripheral ganglionic cells are ordinarily unipolar, and are often 

 in connection with nerves. The anterior median nerves are one to 

 three in number, there is a paired lateral anterior and a similar 

 posterior nerve-trunk. The distribution of these nerves is described. 



The account of the gcnit.il organs commences with a discussion of 

 the so-called ligament, the muscular nature of which has been already 

 recognized by Greof ; it forms a closed cylinder with a simple wall, 

 the histological structure of which is similar to that of the muscular 

 layers of the body ; the account of the genital organs is very full. 



In a concluding note Siifftigen directs attention to a recent paper 

 by Mf'guin, with many of whose results he does not find himself in 

 accord. 



• Morphol. Jahrbucb, x. (1884) pp. 120 71 (4 pla.). 



