190 



CHAS. B. WILSON. 



9. The stomach walls contain numerous gland-cells, which 

 are flask-shaped, with the neck of the flask pointing inward. 

 The inner surface of both stomach and intestine is covered 

 with cilia, and at their junction is a large sphincter muscle 

 which controls the passage of the food particles and waste 

 material. 



Addenda. 



Since the foregoing went to the printer I have received an 

 article entitled " Development of the Pilidium of Certain 

 Nemerteans,'' by W. E. Coe. 



This excellent paper discusses briefly the segmentation, 

 gastrulation, and pilidium stages in Micrura cseca, Cere- 

 bratulus Leidyi, and C marginatus. 



Together with the present paper it was practically finished 

 before either author became aware that the other was work- 

 ing upon the subject. The close agreement in the results 

 obtained is all the more gratifying in view of their entire 

 independence. 



I wish briefly to mention the following points : 



1. In segmentation C. lacteus transposes the second and 

 third cleavage planes of the other three species, making the 

 second horizontal and the third vertical. Otherwise the four 

 agree in all essential features of segmentation and gastru- 

 lation. 



2. While Coe has not given the development of the apical 

 plate and the muscular system in detail, it is evident from 

 his drawings that this development in both cases is almost 

 identical with that here given. The arrangement of the 

 parietal muscles, especially in Micrura caeca, is somewhat 

 different from that in C. lacteus, as might be expected. 

 But the mesenchyme cells from which they are formed are 

 evidently smaller than those which form the other muscles, 

 and correspond to the micromesencytes in C. lacteus. 



3. The statements in reference to the presence of nervous 

 tissue are wisely cautious, but it is easy to see that Coe does 



