. Egg maturation, chromosomes, and spermatogenesis in cyclops [microform]. Reproduction; Spermatogenesis; Cyclopes (Crustacés); Spermatogénèse; Cyclops; Reproduction. 'AiimSJ^^MS^ 1: V 24 Chambers: Chromosomes in Cycxops The absence of mitotic figures in the Keimpolster of all sexually mature individuals, and the fact that the Keim- polster is separated from the testis proper by a sharply de- fined boundary, renders likely the supposition that, after producing a numbrr of spermatogonia, it becomes inert and soon disorganizes, the growth of the testis henceforth being due entirely to spermatogo
. Egg maturation, chromosomes, and spermatogenesis in cyclops [microform]. Reproduction; Spermatogenesis; Cyclopes (Crustacés); Spermatogénèse; Cyclops; Reproduction. 'AiimSJ^^MS^ 1: V 24 Chambers: Chromosomes in Cycxops The absence of mitotic figures in the Keimpolster of all sexually mature individuals, and the fact that the Keim- polster is separated from the testis proper by a sharply de- fined boundary, renders likely the supposition that, after producing a numbrr of spermatogonia, it becomes inert and soon disorganizes, the growth of the testis henceforth being due entirely to spermatogonial mitoses. This Keimpolster corresponds to that described by Haecker in Cantnocomptus and is, according to him ('95a), to Amma ('10), and to Krinimcl ('10), the direct descendant of the germ-cells differentiated as early as in the first cleavage of the egg. Lerat ('05) was unable to find a typical Keimpolster in C. strenutis, He describes an apical cell from which he as- sumed the spermatogonial cells were derived. It is much more probable that this "apical cell" is merely one of the spermatogonial cells and that he failed to find the true Keimpolster as it may have been already disorganized in the individuals studied by him. 3.—MULTIPLICATION ZONE. The region following the Keimpolster consists of a large number of proliferating spermatogonia forming a msss of closely appressed cells. Lerat figures this region as a syn- citium. My preparations, however, give clear ividence of definite cell boundaries (Fig. 24). The resting nucleus (Fig. 25) possesses an irregularly blotched chromatic reticulum. Division figures are periodically frequent (Fig. 27). Definite spindle fibres are pla: ily visible. The chromosomes in the equatorial plate are diploid in number and are more or less U-shaped (Figs. 28, 29). The size of the cells varies greatly, owing partly to dif- ference in time of growth and partly to the number of sper- matogonial divisions that the cells have pass
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Keywords: ., bookcentury1900, bookdecad, booksubjectreproduction, bookyear1912
