QUARTERLY CHRONICLE. 45 



1. In all animals in wliicli it has been possible to study the 

 termination of motor nerves, a special organ has been found, 

 named the "motor plate " {phique motrice), at the extremity 

 of the cylinder axis. 2. The union of the nervous element 

 with the muscular bundle is accomplished in the following 

 manner. When the muscular bundle is provided with sar- 

 colemma, and the nervous element with a sheath, this latter 

 becomes fused with the envelope of the primitive muscular 

 bundle, at the point where the nervous element meets the 

 muscular bundle. At this same point, or a little before, the 

 medullary substance stops, whilst the cylinder axis pursues 

 its course, and penetrates the " motor plate." 3. The motor 

 plate is placed beneath the sarcolemma. It presents usually 

 the form of a cone, with its summit directed to the side of 

 the nerve-tube, whilst the base is applied to the primitive 

 muscular fibres. 4. This plate is formed by two superposed 

 and very distinct layers^ especially in those animals provided 

 Avith large " plates," as, for instance, in the torpedo. The sub- 

 stance of the superior layer is granular, that of the inferior 

 layer is jDerfectly homogeneous, and probably it is nothing 

 more than a thickening of the cylinder axis. 5. In the sub- 

 stance of the granular layer of the plate is found, in the 

 torpedo, a system of canals, in which the cylinder axis rami- 

 fies, forming a coarse netAvork. These canals are limited by 

 a sheath, Avhich forms their Avails. 6. When the muscular 

 bundles possess a central canal, the granular substance of the 

 plate is continuous Avith the granular substance contained in 

 this canal. 7. In animals provided only Avith smooth mus- 

 cular fibres the cylinder axis traverses the granular substance 

 of the plate, dividing itself into two filaments, Avhich pass to 

 the tAvo extremities to terminate in the points of the contrac- 

 tile element. 8. Everything tends to the belief that each 

 primitive muscular fibre has but one motor plate. In this, 

 one or several nervous elements can terminate, arising from 

 the subdivision of one and the same nerve-tube. 9. The 

 diameter of the motor plate augments in proportion to the 

 thickness of the primitiA^e muscular bundle. 



In Dr. Beale's new edition of his Avork ' On the Micro- 

 scope,' recently published, a reiteration of his vicAvs Avill be 

 found, and a defence against such attacks as this of Pro- 

 fessor Trinchesc. 



November and December. — 1. " Memoir on the Anatomy 

 and Zoology of the Acari, of the Genera Cheyletus, Glyci- 

 phagus, and Tyroglyphus," byMM.'A. Fumouze and Ch.Robin. 



This is the continuation and finish of a very detailed and 



