ZOOLOGY AND BOTANY, MICROSCOPY^ ETC. 583 



B. Nemathelmintlies. 



Fertilization of Ascaris.* — Dr. N. Kultscliitzky contributes yet 

 EBother account of the phenomena of fertilization in Ascaris megalo- 

 cephala. 



(1) Formation of polar bodies. Boveri's account is confirmed ; but, 

 like Zacharias, the author maintains the presence of two achromatic 

 spindle figures lying beside one another. (2) The modifications of the 

 spermatozoon are described in a few words. Eeason was seen to believe 

 that not the whole chromatin goes to the formation of the male pro- 

 nucleus. (3) Formation and structure of pronuclei. Both appear to be 

 constructed on the same plan. The author notes as new that each has 

 a characteristic nucleolus, sometimes two, rarely three, but the same 

 number always in both. The results being similar, while the com- 

 ponents of the two pronuclei are originally very different, the process of 

 formation is regarded as something sui generis. 



(4) The number of pronuclei is usually two ; very rarely there is only 

 one, somewhat more frequently three. The single pronucleus is 

 probably that of an unfertilized ovum ; the presence of three is perhaps 

 due to the entrance of a bi-nucleate spermatozoon. (5) First processes 

 in development. After the formation of two pronuclei, there is no 

 further change while the eggs remain in the uterus of the living 

 Ascaris. Herr Kultschitzsky is convinced that without exception the 

 karyokinesis of each pronucleus is independent. The attractive spheres 

 of van Beneden belong to the protoplasm, and represent the first hints of 

 incipient protoplasmic division. The changes seen after the formation 

 of the pronuclei pertain strictly to the segmentation. 



(6) Minutiae of fertilization. The essence of fertilization consists 

 in the process by which the sperm-nucleus — an element foreign to 

 the ovum — is modified into an essentially inseparable component, a 

 nucleus of the same. The act is ended with the establishment of the 

 male pronucleus, what follows belongs to development. A fusion of 

 the pronuclei, when such exists (the author doubts it), does not pertain 

 to the strict process of fertilization. 



Intestinal Epithelium of Ascaris.| — Prof. S. M. Lnkjanow has in- 

 vestigated the epithelium of the intestine in Ascaris mystax. He recom- 

 mends strongly double imbedding with a combination of collodium and 

 paraffin, and double staining with hgematoxylin and aurantia. 



Between the cells and the homogeneous membrane below them is a 

 clear space traversed by very fine threads parallel to the long axis of the 

 cells. Externally the cells exhibit filiform processes like cilia. The 

 cells contain granules, in part at least, consisting of fat. The possible 

 physiology is briefly noticed ; certain not very noteworthy variations in 

 the size, position, membrane and structure of the nuclei are noticed in 

 detail ; and the plasmosomata to which the author has recently directed 

 much attention are fully discussed. 



Studies on Gordiidae.i — Prof. F. Vejdovsky has lately had the 

 opportunity of examining a large number of specimens of Gordius 

 tolosanus. He has some evidence as to variability in the arrangement 

 of the cuticular areolae, which he discusses at some length. He does not 



* SB. K. Preuss. Akad. Wiss. Berlin, 1888, pp. 17-21. 



t Arch. f. Miki-. Anat., xxxi. (1888) pp. 293-302. 



X Zeitschr. f. Wiss. Zool., xlvi. (1888) pp. 188-216 (1 pi.). 



2 S 2 



