PLATE IX. 



Mesenchytrczus penicillus sp. nov. 



FlG. I. Section through the somite containing the male-pore, pb., penial 

 bulb, sagittal section; at.gl., prostates opening through the bulb 

 into the atrium ; atr., atrium ; p.gL, penial glands inside the bulb ; 

 sp.s., sperm-sacs; os., ovisacs. 



2. The lower part of the sperm-duct with the four atrial glands opening 

 into the atrium. Letters indicate the same as in fig. i. 



Mesenckytrceus pedatus sp. nov. 



3. Lymphocytes. These are of very large size and in this respect dif- 

 ferent from most other species of the genus Mesenckytrceus. 



4. Section through the atrium, showing the inner epithelium, the 

 muscles, and the outer epithelium. There are no prostates in the 

 species. 



5. Longitudinal section through somite xn passing through male- 

 pores, atr. , atrium; l.ch., lower chamber of the sperm-duct, a 

 secondary atrium ; p.blb., penial bulb containing unicellular glands ; 

 ac.gl., accessory glands opening at the apex of the penial papilla; 

 sp.d., sperm-ducts; s#.s., sperm-sacs; int., intestine (the dark lines 

 are blood vessels). 



6. Cross-section through male-pores more highly magnified than in 

 the last figure. 



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