1907.] NATURAL SCIENCES OF PHILADELPHIA. 147 



slightly to the left in order to skirt the p-aiiular gland, and then by a 

 fairly direct route leads into the bases of the copulatory organ. A 

 short distance from its entrance into this last-named organ it combines 

 with the short duct from the granular gland. 



The copulatory apjiaratus is a cylindrical body of comparatively 

 large size, occupying the midline and all the available space between 

 the body walls. Its inner third is spongy in character and is pene- 

 trated by a single canal, the ductus ejaculatorius, which continues to 

 the exterior. The remaining two-thirds, constituting the eversible 

 portion, is provided with powerful muscular walls and is lined with a 

 multitude of spines which belong to three distinct classes (fig. 5). 

 Those adjoining the outer opening, and consequently basally situated 

 when the penis is protruded, appear in sections to be at least eight in 

 ninnber. Of these two are of large size, hook-like (fig. 6), and are 

 clearly seen in surface views to be symmetrically disposed on each side 

 of the midline. The other six, or possibly eight, are considerably 

 smaller, less curved, and although not clearly visible in surface views 

 appear likewise to be symmetrically disposed a short distance within 

 the external opening. The second type of spine is the smallest and the 

 most abundant and occurs throughout the greater part of the penis. 

 Each is somewhat spindle-shaped and the free end is slightly hooked 

 (fig. 3). Toward the inner end of the eversible portion this type of 

 spine shades into others of similar form, but of a greater length and of a 

 somewhat more slender appearance. At the extreme inner end, the 

 tip of the fully extended organ, these slender spines become larger and 

 more highly cuticularized, and their distal halves assume the brownish 

 yellow tint of the first type. Among these are several larger, toothed 

 spines which are represented in fig. C. 



Lang maintains that each of the spines in Planocera graffii is merely 

 a modified epithelial cell, and judging from his figure (fig. 4, PI. 10) 

 all are of the same character and are similar to the smallest type in the 

 present species. While this view appears plausible at first sight, there 

 are reasons for believing that it does not express the true state of 

 affairs in PL hawaiiensis. Certainly it cannot be held that the huge 

 spines of the first and third types are each a modified epithehal cell. 

 On the other hand each presents the appearance of being a cuticularized 

 papilla, possibly covered with many epithelial cells, though no cell 

 structure now exists, and penetrated by a connective tissue core which 

 clearly shades basalwards into the unmodified filjrous substance of the 

 penis. Furthermore, while each of the smaller spines may be the pro- 

 <luct of a single cell, there is little indeed in the adult condition to 



