ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 661 



the stimulus to the operation of which, in the absence of rotation, is 

 gravity. 



A short account is given of the effects of nerve-poisons on the 

 Echinodermata, the poisons tried being chloroform, caffein, nitrite of 

 amyl, chloral hydr te, alcohol, strychnia, nicotin, curare, digitalis, 

 and cyanide of potassium. 



Organization of Echinoderms.* — E. Perrier states that the studies 

 of several years have led him to very different results as to the struc- 

 ture of the arms of Comatulids, as compared with those obtained by 

 Dr. Carpenter, and since discussed and variously interpreted by P. H. 

 Carpenter, Liidwig, and others. Perrier's observations have been 

 chiefly made on young or re-developing arms, while those of the 

 writers just named have been made on fully formed arms. 



Ludvvig has described, in Comatulids, a complicated circulating 

 apparatus, the centre of which is formed by a remarkable organ, which 

 is variously known as the heart or the dorsal organ, and which has 

 been thought to correspond to the so-called heart of the Echinozoa. 

 Perrier believes that he has demonstrated that this organ in Asteroids 

 and Echinoids is of a glandular nature, and he finds that in Crinoids 

 it has the same structure as in other Echinoderms, and should, as in 

 them, be spoken of as the ovoid gland. As seen in the pentacrinoid 

 stage of a Comatulid it forms a fusiform body, continuous with the 

 axial cord of the stalk ; in an adult Comatulid it is set on one of the 

 horizontal lamellae of the chambered organ, the nervous nature of 

 which has been insisted on by the Carpenters. Perrier finds that, 

 not only do the fibro-cellular cords which are given off from it present 

 the appearance of true nerves, but that, wherever muscles are found, 

 these muscles are in close connection with the ramifications from it. 

 These ramifications divide into a large number rf cords, the final 

 branches of which terminate in stellate cells, each of which is 

 continued into a muscular fibre. The ramifications are also connected 

 with the fibres contained in the ambulacral tentacles. 



The author thinks that the connection of the axial cords of the 

 arms and cirri with the organs of sensation and of movement confirm 

 the doctrine of Carpenter. So close is the connection between the 

 various tissues of the animal that the nervous system remains in a 

 remarkably non-differentiated condition ; however this may be, the 

 chambered organ ought to be considered as the central part of this 

 system in Crinoids. 



From his studies on the development of the pinnules Perrier finds 

 that, in structure, the arms and pinnules are at first identical. " If a 

 pinnule continues to be developed it becomes a ramification of the 

 arms." Further details with regard to the points here noted in 

 abstract are promised. 



' Challenger ' Ophiuroids.f — T. Lyman's beautifully illustrated 

 volume will be of the greatest service to the student of the specific 

 characters of the Ophiuroidea. In addition to a detailed and technical 



* Oomptes Rendus, xcvii. (1883) pp. 187-9. 



t Zoology, H.M.S. 'Challenger,' xiv. (1882) 386 pp. (48 pis.). 



