478 Prof. S. Apilthy on 



arrangement of the cells which iiavc wandered into tiie 

 original cavity is also wanting. But so soon as a communi- 

 cation was constituted between the cavity of the Blastula and 

 the exterior by means of a mouth-opening, there was also 

 provided the incentive for the immigrant cells to arrange 

 themselves again like an epithelium, this time as an endo- 

 derm, and to pass from the Gymnomyxa form into a Corti- 

 cata phase once more. Thus we already have the true 

 Metazoon, a Coelenterate, or one of the Porifera before us. 

 In this series of stages we nowhere miss the Gastrcea. 



A greater difficulty than those advanced by Frenzel appears 

 to me to consist in the fact that it is not easy to form an idea 

 as to how the single individuality of the Metazoon has arisen 

 from the separate individualities of the Protozoa, which at 

 first composed a loose colony as ancestral form. This, how- 

 ever, is at once a question which directly touches upon the 

 relationship between the soul of the Protozoa and that of the 

 Metazoa, that is really the question of the soul in general! 



Frenzel finally observes something also in the development 

 of SaUnella which is said to be difficult to harmonize with 

 our previous knowledge. lie speaks of a hypotrichous Infu- 

 sorian-like unicellular animal, which he regards as the LARVAL 

 STAGE of SaUnella. " This nevertheless leaves a difficulty of 

 considerable importance to be surmounted," he adds, '■' in that 

 the transition from the single cell with intra-cellular diges- 

 tion to the adult animal with extra- cellular digestion is enig- 

 matical and completely unexplained." I would not consider 

 this phenomenon to be so very enigmatical, even should the 

 fact be established that the digestion of SaUnella is really 

 enzymatic, and not intra-cellular, like that of the majority of 

 the lower Metazoa. This point, however, has already been 

 sufficiently disposed of. Let us at once proceed to consider 



WHETHER A UNICELLULAR ANIMAL, WHATEVER ITS STRUCTURE, 

 can be considered AS THE LARVA OF A MULTICELLULAR FORM. 

 That stage in the ontogeny of the multicellular animal 

 which, while still unicellular, immediately precedes the multi- 

 cellular condition, and is therefore the highest unicellular stage, 

 wc term, whether fertilized or unfertilized, the ripe EGG-CELL. 

 In the case of SaUnella we have before us — if I rightly com- 

 prehend the meaning of a phenomenon observed by Frenzel — 

 the ])roduct of an act of copulation, we might say a zygo- 

 spore ; there can in this case be no question of an actual 

 egg-cell, for there is no difference to be observed between the 

 two eo})ulating cells, and in fact in SaUnella there are no 

 special reproductive cells at all. All the cells in the body 

 have the power of nniltiplying the species, and, singularly 

 enough, the colony does not first relapse into its constituents 



