ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 423 



With regard to the affinities of the Echinorhynchi, reference should 

 be made to the remarkable form Paracloxites discovered by Lindemann ; 

 in it the body is flattened, and divided into distinct rings, of which all 

 but the first and last three are similar in character. The proboscis and 

 its receptacle in the first ring are like those of other Echinorhynchi ; there 

 is a pair of ovaries in every ring, and they open into two longitudinal 

 lateral canals ; the male organ is found in the same individual, and con- 

 sists of a long tube which arises from the floor of the receptacle, and 

 has a swelling in each ring. The oviducts and the efferent canals open 

 to the exterior by a single duct. E. roseus differs only from Para- 

 doxites by the absence of rings. Notwithstanding the incompleteness of 

 our knowledge of this form we cannot doubt its affinities to the Cestoda. 

 If it should be proved that Paradoxites is not an ancient form, then the 

 origin of the Echinorhynchi must be sought for in oligomeric worms, 

 such as the Gephyrea, and the lemnisci may be regarded as segmental 

 organs. But the pressing point is, obviously, further study of Para- 

 doxites. 



Fertilization and Segmentation in Ascaris megalocephala.* — Prof. 

 E. van Beneden publishes a preliminary account of his further researches 

 on the ova of Ascaris megalocephala. These have been made in association 

 with M. Ad. Neyt, well known for his applications of photography to 

 microscopical and astronomical purposes. He has succeeded in obtain- 

 ing a series of about 1200 photographs of all the details of maturation, 

 fertilization, and karyokinesis. Prof, van Beneden has for two years 

 been making use of a more rapid and satisfactory method of fixing and 

 hardening his objects. f 



From the first, two nuclear elements can be seen in the ova. The 

 moment when the male pronucleus is formed at the expense of the small 

 chromatic nucleus of the sperm coincides exactly with that at which the 

 female pronucleus is formed from the two chromatic rod-like elements 

 which result from the second pseudo-karyokinetic figure. At the 

 moment of origin the male pronucleus is enveloped in the degenerate 

 residue of its protoplasmic body which does not lose itself in the egg- 

 protoplasm, but forms a definite layer round the male pronucleus, 

 becoming gradually reduced to a globule, and finally being digested 

 away. With the staining reagents above noticed the protoplasmic body 

 becomes brown, the chromatic elements green, the vitellus almost colour- 

 less. Before the male pronucleus has freed itself from its degenerating 

 mantle, the female pronucleus is formed as a reticulate nucleus near tho 

 second polar body. The chromatin, at first homogeneous, resolves itself 

 into a network of granules united by filaments ; from the periphery of 

 the two rods issue small tracts of achromatic granules united in 

 filaments ; the rods increase rapidly in volume, and invade the surround- 

 ing clear space. A discussion of the value of his method, and of the 

 possibilities of error, is also given. He then proceeds to describe his 

 results at length. 



I. Formation of Pronuclei. — The origin of one of these from tho 

 nucleus of the sperm, of the other from the residue of the germinal 

 vesicle, is described as in the first classic research, which in this particular 

 is left unaltered. 



• Bull. Acad. R. Sci. Belg., xiv. (1387) pp. 215-91 (6 pis.), 

 t Of. infra, Microscopy 0. 



