No. 3.] ORGANS IN PHASCOLOSOMA GOULDII. 383 



classification has no reference to the distribution of these 

 bodies ; for in the integument of the worm glandular and non- 

 glandular organs are found intermingled with one another, with 

 no definite arrangement. 



Organs of the First or Nofi-Giandular Class [First Type). 



The organs of this type are most abundant on the anterior 

 end of the introvert, in which region, indeed, none of the other 

 types are found. Above each organ the cuticula is much re- 

 duced in thickness, the reduction being made from the inner 

 surface. Each organ has quite a large number of sensory cells, 

 as many as six or seven of these often responding to the blue 

 stain. Moreover, in nearly all cases there is evidence that 

 there are sensory cells which have not taken the stain or which 

 have taken it only in a slight degree. A drawing of one of 

 these organs (PI. XXXIV, Figs. 3 and 10) shows that the group 

 of sensory cells is situated near the middle of the flask, and that 

 the long axis of the individual cells is perpendicular to the ring 

 muscles. The sensory cells are spindle-shaped and are all 

 bipolar. The peripheral process is stouter than the central 

 process, and at a short distance below the cuticula, is somewhat 

 broadened and thickened, making a club-shaped end. From 

 this expanded end a slender sensory hair ascends to the cutic- 

 ula and passes through it to the exterior. It is only in exceed- 

 ingly fortunate preparations that the sensory hairs have retained 

 the stain, but it is probable that in all cases such hairs are 

 present. The central processes from the sensory cells emerge 

 from the flask in one bundle, pass inward across the band 

 of circular muscles, and enter one of the main nerves coming 

 from the ventral cord. So far as these central processes were 

 followed they were never seen to branch. 



Organs of the First or Non-Glandular Class (Second Type). 



These organs, like those of the first type, are strictly non- 

 glandular and evidently have some marked sensory function. 

 Like those of the first type, again, they are each flask-shaped. 

 They are to be distinguished, however, even under a low power 



