202 M. A. Stecker on the Development 



the peculiar round bodies (spheres) which, as he says*, occur 

 in the protoplasm of the spider's ovum, are wanting in Che- 

 lifer (as in the ovum of the true scorpions). But I believe 

 that in the secondary deutoplasm-spheres we may see an 

 analogue of the spheres observed by Clapar^de f, Zalensky |, 

 Balbiani §, and others, but first correctly understood as deuto- 

 plasm-spheres by Ludwig ||, and which afterwards become the 

 peculiar flakes {Schollen). 



The freshly deposited Qgg^ attached to the ventral surface 

 of the mother, measures from 0*095 to 0*12 millim., is of an 

 elongate ovate form, and presents, besides the so-called vitel- 

 line membrane secreted by the ovicell while still in the ovary, 

 a secondary layer, which was separated from the protoplasm 

 layer of the ovarian tube H during the deposition of the Qgg 

 (at least this is the only possible explanation of it). Like the 

 secondary external membrane of the eggs of PMlodromus 

 investigated by Ludwig **, this is divided into rounded areas, 

 which give the entire membrane an elegant cellular appear- 

 ance, and are produced by the fine granules of the protoplasm- 

 mass being arranged in circles. They were observed and 

 figured by Metschnikoff ff, who, however, says nothing about 

 their origin. 



The &g^ in this stage is now subjected to a new and very 

 important process : the segmentation, which closely resembles 

 that of Chelifer, commences; and here also the nutritive vitel- 

 lus undergoes a total segmentation {amphigastrula, Hackel \X) . 



* "Entw. des Chelifer,'' I. c. p. 575; "Embr. des Scorpions," I. e. 

 p. 208. 



t E. Claparede, " Recherches sur revolution des Araign^es," Utrecht 

 1862, in Natuurk. Verb. Utrechtsch Genootschap van Kunsten en 

 Wetensch. Deeli. 



I Zapiski Kieffskaro Obshtchestva Estestvoispitatelei, torn. ii. (1871) 

 pp. 1-72, vrith 3 plates. 



§ Balbiani, " Memoires sur le developpement des Araneides," Ann. des 

 Sci. Nat. 5« ser. Zool. tome xviii. (1873) art i., with 15 plates. 



II Hubert Ludwig, " Ueber die Bildung des Blastoderms bei den 

 Spinnen," Zeitschr. I'iir wiss. Zool. Bd. xxvi. (1876) pp. 470-485, pis. 

 xxix., XXX. 



^ The inner wall of the ovary in Clithmiius is lined by a layer of homo- 

 geneous protoplasm-mass in which numerous nuclei are imbedded, but 

 without the individualization of any special portions of protoplasm around 

 the nuclei {syncytium, Hackel). 



** Ludwig, /. c. p. 471, pi. xxx. 



tt Metschnikoff, " Entw. des Chelifer,'" I. c. p. 516, pi. xxxviii. 



Xt E. Hackel, "Die Gastrula und die Eifurchung der Thiere," Jenaische 

 Zeitschr. fiir Natm-w. Bd. x. (1876) pp. 61-167, pis. ii.-viii. (see pp. 67 

 and 83 et seqq.). 



Hackel well remarks that the unequal segmentation occurs in by far the 

 greater number of Arthropoda, but in most cases has not been accurately 

 enough observed. 



