468 J. RUNNSTROM 



and protein, cf. [27]. We call the active agent "jelly precipitating factor" 

 which may be identical with the antifertilizin of F. R. Lillie [14]. Later on 

 Hagstrom found that direct treatment of the surface of intact unfertilized 

 eggs with ribonuclease also causes the precipitation of the jelly coat. 

 Ribonucleoprotein granules are thus probably present also in the surface 

 of the eggs as was earlier suggested by the work of Lansing and 

 Rosenthal [12]. 



In phase contrast it is easy to see dark spots in the surface layer of the 

 egg, the so-called hyaline layer. The spots represent evidently groups of 

 ribonucleoprotein granules. Upon brief treatment with ribonuclease in sea 

 water they vanish. The hyaline layer is rich in acid mucopolysaccharides. 

 The structureless layer is perforated by numerous villi. These villi are the 

 carriers of the ribonucleoprotein granules which are attached to vesicles 

 or tubules. According to my view the microsome system extends into the 

 tips of the villi. Electron micrographs put at my disposal by my colleague 

 B. Afzelius are in keeping with this view.* 



Under certain conditions the villi may be strongly enlarged and in such 

 giant villi both groups of dark granules and of lipoprotein tubules w^ere 

 observed. In certain cases the tubules could be followed as continuous 

 structures deeply into the endoplasm where they were seen to be connected 

 with the astrospheres in the architecture of which tubular lipoprotein 

 structures seem to play a role. One may assume that the microsome system 

 of the villi control the state of the cell surface. 



At the segmentation the hyaline layer concentrates to the equator of the 

 egg along with the villi and their content of microsomal elements. A release 

 of a gelating agent occurs equatorially at the onset of segmentationf [24]. 



Cell differentiation is also on the programme for the discussion today. 

 Dr. W. F. Loomis has discovered how a relatively simple factor, carbon 

 dioxide, may induce the formation of genital cells in the fresh water 

 cnidarian. Hydra. 



If I may be allowed to persist in talking about our own results, I shall 

 go back to the experiments on the gelating action of trypsin on the sea 

 urchin eggs. Relatively few of the eggs develop that were exposed to 

 io~^-io^^ ^'1, trypsin. If we examine the larvae obtained after about 24 hr., 

 cf. Fig. 2, we can distinguish three types : (a) rather normal larvae with 



* It may be referred to Fig. 22 in [27]. Vesicular and tubular structures are 

 seen in the villi, cf. also Mercer and Wolpert [19]. In the electron micrograph [27] 

 150 A granules could readily be seen to surround at least some of the vesicles. The 

 reproduction does not give justice to the original in this respect. What is seen in 

 phase contrast as dark spots corresponds certainly to groups of granules surround- 

 ing a vesicle. 



f This is also the stage in which the groups of ribonucleoprotein granules are 

 best observed in phase contrast. 



