430 W. A. HASWELL. 
cells combining to form a network, occur in other Acela. 
Von Graff, who re-directs attention to these in a recently 
published work (17) on the Turbellaria as parasites and 
hosts, does not express any definite opinion as to their 
nature, though he rejects his previous supposition that they 
might have some connection with the so-called “ crystalloids” 
(really spores of a Sporozoan) occurring in certain fresh-water 
Rhabdoceeles. But the regular distribution of the bodies in 
question, to form a bilaterally symmetrical pattern, and their 
restriction, or virtual restriction, to the dorsal surface, seem, 
with the other points already referred to, to render it evident 
that we have here to do with a normal constituent of the 
epidermal layer, and one which may be best regarded as a 
peculiar variety of pigment cell. 
Here and there a little process or papilla projects on the 
surface of the epidermis; each of these is a mass of rhabdites 
projecting through an aperture in the epidermal layer—the 
opening of the duct of a rhabdite-forming gland. The rhab- 
dites (fig. 5) are of two kinds,—shorter, fusiform, and longer, 
very slender. ‘l'hey often collect in packets in the ducts near 
‘heir extremities. ‘I'he ducts are sometimes longer, sometimes 
shorter—the glands being sometimes near the surface, some- 
times more deeply sunk. When the rhabdites are discharged 
a sticky gelatinous fluid is poured out with them, and by 
means of this secretion the animal is able to adhere with 
surprising firmness to a smooth surface, quite a strong Jet of 
water being necessary in order to displace it. In this the 
whole ventral surface shares; but the posterior processes 
maintain their hold most tenaciously. Rhabdites are given 
olt freely on the dorsal as well as on the ventral surface. 
When there is some irritant present in the water, a rapid 
discharge takes place, and the animal becomes enclosed in a 
whitish covering, which soon stiffens to form a protecting 
cocoon, This is, in all probability, the main function per- 
formed by these integmentary glands. But it is quite likely 
that the secretion may have some effect in entangling, and 
