964 RECORD OF CURRENT RESEARCHES RELATING TO 



canal wliich are riclily supplied with chyme. It is probable that the 

 ctenophoral vessels of the Ctenophora, which are comparable to the 

 radial canals of the Medusae, were, like them, primitively placed just 

 below the ectoderm, and that they owe their changed position to the 

 development of gelatinous matter in the disk. In their change in 

 position they would seem to have been accompanied by the genital 

 organs. 



Structure of the Neuro-muscular System. — After a short account of 

 the investigations of earlier observers, and a somewhat more detailed 

 notice of those of Eimer, the author states that in general he finds 

 himself in agreement with the latter. He is of opinion that there is a 

 true nervous system, the elements of which are to be found in the 

 gelatinous layer ; and he considers that they are diffused through the 

 body and do not exhibit any distinct centralization. Such physiolo- 

 gical observations as he has been able to make are found to be in con- 

 cordance with the results of Eimer. At the same time the agi'ce- 

 ment is only of the most general character. The varicosities which 

 Eimer regards as forming structures allied to ganglionic cells are 

 regarded by Hertwig as being artificial products. Yet again, Eimer 

 finds no nerves in the ectoderm, while Hertwig believes that he has 

 found a well-developed nerve-plexus in that layer. 



The author next compares his results with those of Chun, and 

 then proceeds to say that the nervoixs system of the Ctenophora con- 

 sists of an ectodermal and a mesodermal portion. The former has 

 the character of a ganglionic plexus which lies just below the epithelium 

 and is equally distributed over the whole surface of the body. In 

 Beroe it may also be followed on to the stomach, where it takes up a 

 position between the gelatinous and the muscular layer, in consequence 

 of the great development of this latter. Only a small number of nerve- 

 fibrils are given off, and these branch and anastomose very consider- 

 ably. Nowhere in the plexus is there any indication of a commence- 

 ment of any centralization. From a priori considerations it is to be 

 imagined that there is some connection between uuo elements of the 

 plexus and the sensory cells of the auditory vesicles and the polar 

 areas, but this has not yet been demonstrated. In no one case was it 

 possible to detect nervous processes passing to the cells. The same 

 is true as regards the tactile cells, which are found everywhere in the 

 epithelium, and especially in the region surrounding the mouth in 

 Beroe. The tentacular apparatus forms a special division of this 

 neuro-muscular system. The ectodermal muscles are here of enormous 

 length, and pass at their base into epithelial cells. To the surface of 

 this layer they are set perpendicularly. 



The mesodermal portion of the nervous system would appear to 

 consist of a very large number of very delicate fibres, which are, at 

 points, provided with spindle-shaped nuclei, and are invested in a 

 neurilemma. Like the muscular fibres, they pass separately into the 

 gelatinous layer, and end by branches in the epithelium. The pro- 

 cesses by which they are connected with this layer are probably de- 

 rived from the ectodermal plexus, but of this there is no certain 

 evidence. There does not seem to be any regularity in the mode of 



