ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 593 



but soon break up into fine nerve-fibres, whicb course in various directions, 

 forming at last a plexus of the finest nerve-fibrils. The whole arrangement 

 of this terminal nerve-plexus agrees in almost every detail with the epidermal 

 plexus of the peripheral nervous system of Sagitta. 



The plexus is especially thick in the region of those peculiar dermal 

 structures which so richly cover the body of Halicryptus, and these, there- 

 fore, may be definitely regarded as tactile organs. True unicellular glands 

 are found abundantly among the epidermal cells, just as in Oligochseta. 

 The intestine has a longitudinal and a circular layer of muscles, while just 

 beneath the epithelium there is a layer of very fine muscular fibres, which 

 extend in all directions. They agree in structure with those of the body 

 in forming a tube which is filled with protoplasm, and has walls formed by 

 fine fibrils. The enteric epithelial cells are extraordinarily long, and have 

 at their upper ends a knob-like swelling, with a fringe of very short and 

 fine cilia. The whole wall is traversed in all directions by a system of very 

 fine canaliculi, which have, perhaps, the function of chyle-vessels. Among 

 the coelomic corpuscles some are small and livelily amoeboid, and others 

 larger and non-amoeboid. They appear to be derived from the numerous 

 amoeboid connective-tissue cells, which are not only able to move about 

 among the tissues, but to pass into the coelom. Between these and the small 

 forms there are various intermediate stages. It may be remembered that 

 Kukenthal found the same mode of origin for the lymphoid cells of 

 Annelids. 



B. Nemathelmintlies. 



Process of Fertilization in Ascaris megalocephala.* — Dr. 0. Zacharias 

 has made use of some new methods of investigation for the purpose of study- 

 ing the finer processes in the fertilization of the egg of Ascaris megalocephala, 

 as he suspected that Nussbaum and van Beneden had had to do with injured 

 ova. By this new method, in which he successfully hardens the ova in two 

 hours, and preserves them without any shrinking of the yolk, he has been 

 able to obtain a series of the intermediate stages in the formation of the 

 pronucleus which were as yet wanting. The results agree with the theory 

 of 0. Hertwig as to the fusion of the genital products, and give a fresh sup- 

 port to it. What Prof. E. van Beneden took for pronuclei are reported to 

 be already conjugated nuclei. A full account of the results is promised. 



Revision of the Gordiidse.t — M. A. Villot discusses and describes nine 

 of the species of the genus Gordius. Four of these — G. affinis, G. alpestris, 

 G. gemmatus, and G. Bouvieri — are new. The last named is alone an exotic 

 form ; all the rest were collected in the neighbourhood of Grenoble. 



The author expresses his dissatisfaction with most of the descriptions of 

 preceding authors. The variations in length and breadth are so great that 

 these characters must not be supposed to have any specific value. The 

 coloration of the integument depends on the extent to which chitinization 

 has proceeded ; in all species young individuals are of a uniform milk-white 

 colour, and the females arc always less deeply coloured than the males, and 

 after the deposition of ova their integument has almost always the trans- 

 parency of glass. The possession of a buccal orifice, and the division of 

 the body into rings are youthful characters, of which no traces are left in 

 old individuals. The form of the two extremities is really of specific im- 

 portance, but even here attention must be given to the age of the specimens. 

 The bifidity of the caudal extremity of the males is a sexual character, and 



* Zool. Anzeig., x. (1887) pp. 164-6. 



t Aim. Sci. Nat., i, '.1887) pp. 271-318 (3 pis.). 



