206 M. A. Stecker on the Development 



plasm-spheres ; these collect round the germinal vesicle, which 

 is situated in the centre and surrounded bj a layer of proto- 

 plasm. The germinal vesicle disappears. The primary deu- 

 toplasm-spheres become secondary ones — the true nutritive 

 vitellus, which contains in its interior first a brown nucleus 

 consisting of granules separated from the protoplasm, then a 

 layer of protoplasm, and lastly a layer of untransformed 

 primary deutoplasm-spheres. Now the segmentation takes 

 place, and is total : the nutritive vitellus divides into two, four, 

 and finally eight large vitelline cells ; at the same time the 

 nucleus and the protoplasm also divide. An internal cavity 

 also is formed, in which a portion of the protoplasm is pre- 

 served ; after the completion of the segmentation this separates 

 outwards and envelops the nutritive vitellus. With the proto- 

 plasm the primary deutoplasm-spheres confined in the same 

 cavity also come into view ; and these then form an albumi- 

 nous-looking layer at the periphery of the egg. Next the 

 nuclei of the individual vitelline spheres break up partially 

 into a number of granules, and work, with the protoplasm sur- 

 rounding them, out of the vitelline cells, which are constantly 

 more and more reduced, arrange themselves superficially, be- 

 come individualized as independent cells, and thus form the 

 blastodermic vesicle. 



If we now compare these details, especially with respect to 

 the formation of the blastoderm, with the results of Ludwig's 

 investigations of the formation of the blastoderm in the egg 

 of Philodromus^ ^ we at once see the great analogy that exists 

 between the two processes ; for Ludwig's deutoplasm-spheres, 

 which unite into columns and afterwards develop into the 

 peculiar flakes (SchoUen), correspond to the secondary deuto- 

 plasm-spheres of Chthonius. The nuclei originating in the 

 central substance of the rosettes (the protoplasm of Chthonius), 



* We may be permitted liere to recapitulate briefly Ludwig's extremely 

 interesting results (/. c. p. 479) : — " The germinal vesicle disappears ; the 

 deutoplasm-spheres unite to form columns, which group themselves 

 radiately around a central protoplasmatic substance and are held together 

 by it ; this rosette divides binarily into several rosettes of division ; nuclei 

 originate in the central substance of the rosettes; the nuclei with the 

 protoplasm surrounding them work out of the rosettes, which during 

 their division are constantly pressed more and more towards the peri- 

 phery, arrange themselves superficially, and form by mutual approxima- 

 tion and limitati9n the blastodermic vesicle ; the portions of deutoplasm 

 which have become flakes (SchoUen) sink back into the interior of the 

 egg." 



