584 SUMMARY OF CURRENT RESEARCHES RELATING TO 



agree ^^•ith Yillot's conceptions of the limits of species of the genus 

 Gordins. The coolom of all the females examined was found to be very 

 well developed, and in no case was the anterior or median region filled 

 by the so-called cellular tissue ; but this was present in the hinder part 

 of the body-cavity. In no individual were the elements of the peritoneal 

 epithelium found dividing, from which it may be concluded that there is 

 no formation of cell-tissue at the time when the ova are being produced. 



A peculiarity was noticed in the peritoneal cells ; beside the nucleus 

 there is a small body which is only faintly coloured by picrocarmine ; 

 it has an irregular contoiir, and is generally lobate ; its contents are 

 almost homogeneous, and its size is 0" 003-0 '005 mm. It is impossible 

 to say definitely what this body is, but it ai>pears to be a thickened 

 portion of the cell-substance. 



The mesenteries are mere continuations of the modified peritoneal 

 epithelium. 



The author makes some additions to his earlier account of tho 

 nervous system. He has already shown tliat the ganglion-cells only 

 occupy the lower part of the ventral cord, and that in Gordius Prcsslii 

 there are transverse commissures which, in some sections, arc to be seen 

 in the dotted substance. In G. tolosauus he finds that some sections 

 show on either side a ganglionic cell which gives oft' a process to the 

 dotted substance ; the two processes fuse and form the transverse com- 

 missure. As this is again repeated after a number of sections in which 

 it is not to be seen, we may suppose that the lateral ganglionic cells 

 and the transverse commissures are repeated in a definite order ; this is 

 a fact of some significance in the morphology of the Gordiidaj, especially 

 when we consider that the ovaries are arranged symmetrically in the 

 body-cavity. 



The author at one time believed that he could recognize the 

 peripheral nervous system in the so-called neural lamella, but with more 

 satisfactory material he has been able to see that in some transverse 

 sections there is no laiuella. It must, therefore, be concluded that tho 

 peripheral nervous system is not represented by a continuous median 

 lamella, but by separate nerve-stalks closely succeeding one another. 

 Separate ganglionic cells send off their processes towards the hypodermis 

 inclosed in a homogeneous sheath-like membrane, which appears to be a 

 continuation of the capsular investment of the ganglionic cells. 



The author has altered his view as to the nature of the so-called 

 dotted substance, which he regarded as fibrillar or fibrous substance, as 

 he has now convinced himself that there is a real network. He proposes 

 to speak of the substance as "neural reticulum," or simply "nerve- 

 network." He believes that the neural reticula of Mollusca, Arthro- 

 pods, and Worms are completely homologous structures. To understand 

 this substance properly, it. must be examined during the course of its 

 development ; the author has done this in Oligochasta, with the following 

 results : — In each half of the ventral cord, four upper cell-rows of the 

 primitive ganglionic rudiments take part in forming the nervous tissue. 

 As the cells increase in size their membranes become absorbed, and in 

 each half of the ganglion we get a syncytium with four nuclei. The 

 latter lose their membranes and swell uj) considerably, so that the 

 regularly disposed nuclei touch. The swelling of the nuclear substance 

 continues, the nucleoli become absorbed, and the nuclear reticulum 

 becomes very distinct. The cytoplasm which surrounds them forms at 



