ON UEVELOrMEXÏ ETC. OF THOKOXIS. 511 



i« situated, not in the eeiitrc, luit near the }teiiphery, is al- 

 ways in tlie nieta- ur ana-phase of Karvokinesis (fii;". 17). Tn 

 sncli an ovum the ehroniosonies are constantly fcund to he i^ix in 

 nuiiiher, each ])ein_u- dinnh-hell shajted witli the t\V(j ends directed 

 towards the poles. Fii;-. 18 represents a portion ot" the section 

 pussin,!;' through the eipiatorial })lane (jf the nncleai' li,L;ure. It is 

 evident that these eggs are in preparation for the extrusi(ai of tlie 

 first polar glol)ule. As shown in the ahove figure, the finely 

 granular protoplasm of the vitellus contains thickly and uniformly 

 distriljuted yolk granules, which have a strong affinity for eosin. 



That the eggs in question are mature is further demonstrated 

 Ity the fact that I succeeded in artificially fertihzing them and in 

 reai'ing out of them normal endjryos which grew to certain ad- 

 vanced stages of development. 



If we now examine the emlnyonal masses, which, as has 

 heen mentioned, are found attached one on each side of the ten- 

 tacular crown of the adult Phoronis, we find that the end)ryos 

 which are farthest away from the nephridial pores are the most 

 advanced in development and that they are found in successively 

 younger and younger stages as we a})pr()ach the pores, until we 

 reach such eggs as have just l)eeu fertilized or perhaps even such 

 as have not yet Ijcen fertilized at all. But even the youngest eggs 

 found in the mass present an appearance very different from 

 those found in the l)ody-cavities, the former being invariably at 

 a stage after the ex[)ulsion of one or two polar glof'ules. In the 

 e'S'i taken frtan the mass and shown in liü'. VJ, two iiolar globules 

 have already been formed ; these nvv situated close together just 

 inside the vitelline mend)rane. 



On the other hand, if we examine by means of serial sections 

 through the ])osterior region of an adult, where the stomach and 



