ALEXANDROMENIA VALIDA. 143 



condition contain not less than 100 cells. Of these fully twenty-five are located 

 in the stalk while the remainder hold positions in the expanded portion. This 

 last named section is relatively compact and lacks the spaces and pseudopodia- 

 like processes characteristic of the majority of Solenogastres. The cells com- 

 posing it are of two distinct types, one containing small spherical dense nuclei 

 and another in which the nuclei are of twice the diameter of the first, and stain 

 but faintly in haematoxylin. The cell boundaries are invisible and it is conse- 

 quently impossible to determine if these dilTerences are correlated with others. 

 The cells with the small nuclei contain a few relatively large yellowish pigment 

 granules, and there is some evidence, though not wholly conclusive, that this 

 secretion is absent from the cells of the remaining type. 



Of the two kinds of spicules the larger (0.189 mm. long) projects from the 

 hypodermis almost at right angles and its pointed extremity projects slightly 

 above the surface of the body. As Plate 37, fig. 11 shows these spicules are 

 hollow and remain constantlj^ in contact with their matrix cells, which are 

 several in number and in their general appearance and relations are not unlike 

 those of P. hawaiiensis. 



The second type of spine is many times more numerous than the one just 

 described. Over the body generally all are of essentially the same size (0.135 mm. 

 average length) and in their needle-like appearance resemble the long spines 

 of Proneomenia, Strophomenia, etc., with which they are probably homologous. 

 Without any very definite arrangement they form several layers parallel with 

 the hypodermis. 



The anterior pedal gland occupies practically all the space between the body 

 and pharyngeal walls between the brain and the radula. The cells are of various 

 sizes but average 0.189 mm. in diameter and are so densely filled with secretory 

 products that all other elements of the cell are invisible. From each a duct 

 leads to its intercellular opening into the anterior end of the ventral furrow. 



The outlet of the anterior pedal gland, the widened end of the pedal furrow, 

 is of large size, and its walls are fashioned into numerous folds (Plate 21, fig. 2) 

 to afford sufficient surface for the exit of the many ductules. On the roof of 

 the cavity two short longitudinal ridges, almost papilla-like, are present and 

 from these numerous much smaller folds extend down the sides of the chamber 

 to the external opening. After treatment with haematoxylin the secretion of 

 the pedal gland becomes almost black, indicating an alkaline reaction, while the 

 cells lining the outlet of the pedal gland (between which the ductules make their 

 exit) are bright pink in color and therefore distinctly acid in their reaction. 



