338 Journal of Applied Microscopy. 



In the spermatozoid are distinguished a true reticulum, " easily seen in the 

 ' head ' and along the periphery of the ' cone,' " and a central refractive body 

 composed of a myosic enchylema which dissolves gradually after entrance into 

 the ovular cytoplasm, thereby unmasking the reticulum in this part of the cone. 

 Boveri, v. Beneden. Kultschitzky, and v. Erlanger have maintained that the 

 whole spermatozoid disappears by this " digesting " action, some of them adding 

 that it furnishes only the needed centrosome. Kostanecki, Siedlecki, and the 

 authors agree that the sperm is neither thus lost nor cast out, but adds itself to 

 the ovum — " impresses its seal " on the egg. As the enchylema disappears the 

 spermatic reticulum fuses with the ovular reticulum in a /A?^v ilu fusion which 

 is filled with enchylematous granules (=Boveri's archoplasm). The trabecula; 

 of the plage dii fusion are seen to be continuous with the cytoplasmic trabe- 

 cukv, and since there is no residual figure — no remnant of the spermatozoid, 

 it must have fused with the egg, the result being an element of mixed nature. 



Segmentation is accomplished under the agency of ''corpuscles," which 

 answer in all but origin to the centrosomes of other authors. There are formed, 

 at the expense of the chromatin of the pronuclei, two to four small bodies figured 

 by others as achromatic nucleoli. These reduce by fusion to one in each 

 pronucleus. They then escape through the nuclear membrane before its disso- 

 lution, and take position at opposite ends of the forming segmentation nucleus, 

 where they function as centrosomes. By chemical influence on the surrounding 

 reticulum, the trabeculae are thrown into radiating fibers, which thus compose 

 the asters and the spindles. The attraction spheres of v. Beneden, thought by 

 him to be permanent, are these aster formations filled with granules. The cen- 

 trosome, having accomplished its purpose, disappears by absorption and new 

 ones are formed by the daughter nuclei for the next segmentation. 



In the variety univalcns, an important point is noticed in the re-formation of 

 the nuclei. Each nucleus gets a male and a female V, which come in the course' 

 of regeneration to be crossed after the manner of the wickets of a croquet 

 " basket." By disintegration of the middle parts these break in two, and then 

 fuse conjugally (spermatic with ovular portions) to form the nucleinic cord. 

 The disintegrated middle portions form the nucleoli which become the centro- 

 somes of the succeeding cleavage. There is a possibility here of maternal and 

 paternal centrosomes. Subsequently, when chromosomes are formed from the 

 loose skein stage, the division is such that each of the two is again of mixed 

 nature. 



According to the most generally accepted theory of fertilization : 

 (1) the egg and sperm are each something short of a complete cell — 

 the egg lacks a centrosome, the sperm, cytoplasm ; (2) each complements the 

 other, the deficiencies being made good by fusion ; (3) the centrosome is a 

 permanent organ of division introduced by the sperm, and perpetuated from one 

 generation of cells to another by division. The first proposition is refuted by 

 Carnoy and Lebrun, by pointing out that every cell loses its centrosome after 

 division — a centrosome not being found in somatic cells at rest. The ovocyte 

 is therefore not peculiar in this respect. Second, the deficiency could not be 

 filletl by the male element for the reason that it has no centrosome until its 



