PLATE VIII. 



Mesenchytrceus solifugus Emery. 



FIG. i. Cross-section of the atrium, showing the entrance of three of the 

 atrial glands, at.gl.^ atrial glands; cr.m., circular muscles sur- 

 rounding the ducts of the atrial glands at their entrance into the 

 atrium; d.at.gL, ducts of the atrial glands continuing into the 

 atrium ; e$., a thick epithelial layer of cells surrounding the muscular 

 part of the atrium. The inner large cells are strongly charged 

 with eosinophilous granules. Similar granules are found in the 

 atrial glands in large quantities. 



2. A detail of the point of entrance of a prostate in the atrium ; longi- 

 tudinal section. 



Mesenchytrceus fuscus sp. nov. 



3. Anterior somites. 



4. Section through the male-pore, atr., atrium; at.gl., atrial gland; 

 sfd., sperm-duct; p-gl-i penial glands inside the bulb; m., muscles 

 separating the penial glands; c.m., circular muscles surrounding 

 the ducts of the atrial glands. 



5. Cross-section of the atrium showing the entrance of one of the 

 atrial glands and circular muscles surrounding the ducts of four 

 other atrial glands, atr.^ atrium ; at.gL, atrial gland ; spd., sperm- 

 duct; p-gl'i penial glands inside the bulb; *., muscles separating 

 the penial glands; d.at.gl., ducts of the prostate cells. The fine 

 ducts, or prolongations of the unicellular atrial glands, are seen as a 

 mass surrounding the clear glandular epithelium inside the atrium. 



