EMBllYOLOGY Ol'' CLEPSINE. 211) 



(diam.). Examined in a fresh condition and by reflected light, 

 it can hardly be distinguished from the peripheral part ; but, by 

 transmitted light, it appears as a railky white, indistinctly out- 

 lined, central stripe. Along the centre of this stripe is seen, by 

 reflected light, a white, opaque, irregularly outlined substance, 

 which becomes less and less compact from behind forwards. 

 This axial substance, which appears like a white thread under a 

 low objective, consists of yolk-graniUes (" Elementarkorner," 

 Leydig). Before the eggs begin to grow, these granules are 

 comparatively few, and scattered uniformly through all parts of 

 the egg-string; but with the growth of the young eggs they 

 multiply much more rapidly in the axis of the rhachis than else- 

 where, and soon render the larger part of the rhachis opaque. 

 The ground substaiice of the rhachis is a fine granular proto- 

 plasm, which contains besides the yolk-granules (Deutoplasm, van 

 Beneden) some free nuclei, around which 1 have never been able 

 to discover the least trace of cell-limits. Under slight pressure 

 the contents of the rhachis will flow out at any point where the 

 egg-string is broken, showing that it is much less coherent than 

 the— 



£. Perijiheral Part. — The peripheral part treated with 

 osmic acid and carmine appears to be composed of dee])ly 

 coloured crowded oval nuclei ("Ol mm. diam.)., each of which 

 incloses a more deeply coloured nucleolus ("0025 mm diam.). 

 Besides the nuclei are seen small groups of deutoplasmic gra- 

 nules (fig. 58), where in earlier stages only single granules were 

 seen. These groups diminish in frequency and in size as we 

 approach the anterior end where they are reducetl to single 

 granules. We thus have a picture of their different stages of 

 development on one and the same preparation. The nuclei are 

 imbedded in what seems to be a common ground-substance, no 

 cell-outlines being recognisable. The same is true of sections 

 hardened in alcohol. All this would seem to confirm the state- 

 ments of Leydig and Ludwig. That these nuclei are woi free, but 

 the centres of well-defined cells, is proved beyond a doubt by 

 sections of an egg-string treated first with osmic acid (-j-L- per cent. 

 10 — 20 minutes), and then with alcohol, and stained with Beale's 

 carmine. Fig. 57 represents one of these sections drawn with 

 the camera lucida. The cells were on every section remarkably 

 well defined. It can be said, therefore, with certainty, that the 

 peripheral part of the egg-string is composed of ready-formed 

 cflls : this accords fully with the statements of Leuckart. 

 "Whence come these cells? Do they exist first as free nuclei, 

 suspended in tlie protoplasm of the rhachis, and, after assuming 

 the cell-form, pass into the peripheral part? 



Unfortunately my investigations do not furnish sufficient data for 



