84 " V. E. EMMEL 



cive to a more convincing conclusion regarding the problem. 

 The results of such a further study may be presented in the form 

 of two groups of data: the first referring to the character of cer- 

 tain cellular masses found free in the coelomic cavities and the 

 second to the structure of the mesothelium in certain regions of 

 the coelomic walls. 



b. Free cell masses in the coelomic cavities. In addition to 

 single free coelomic cells there are also found certain interest- 

 ing groups or masses of cells (figs. 15 and 16). Such masses are 

 of fairly constant occurrence. Some of them may consist of 

 only two or three component cells (fig. 15) or of a much larger 

 number of cells as in figure 16 which is a section of a mass 

 extending through as many as five sections. 



These masses cannot be said to represent merely a loose aggre- 

 gation or agglutination of otherwise free coelomic macrophags, 

 for upon closer study it may be observed that as a rule their 

 component cells are organized into a definite peripheral or epi- 

 thelial layer with a'n occasional cell more centrally situated. 

 Consequently as seen in section, the larger masses present the 

 appearance of epithelial rings surrounding a lighter and less 

 cellular core. The majority of the cells in these masses, espe- 

 cially the more peripheral ones, are indistinguishable in both 

 nuclear and cytoplasmic structure from the mesothelial of the 

 adjacent coelomic walls. In other words there is every indica- 

 tion that these masses are groups of mesothelial cells in which 

 the mesothelial character of the cells are still clearly evident. 

 Upon the careful examination of serial sections it can also be defi- 

 nitely established that the majority of these masses (such as 

 shown in figs. 15 and 16) are entirely free in the coelomic cavity, 

 nor do they present the appearance of having been artificially 

 separated from the coelomic walls. Occasionally such masses 

 are, however, still attached to the coelomic wall and their rela- 

 tions in this case are such as to indicate that the mesothelium 

 has grown out into the lumen of the coelom in the form of a 

 papillary projection which may subsequently become detached. 

 We have therefore, what appears to be a clear case of the actual 

 separation of mesothelial cells from the coelomic wall and lying 

 free in the coelomic cavity. 



