W. H. Leigh-Sfiarpe 
279 
The Cocoon glands. These glands, which occur in most Hirudinea, 
however nowhere in such development as in the Ichthyobdellidae, 
open always on the clitellum; wherefore they were called by Bourne 
(1884) clitellar glands. He states that in Piscicola they are “very 
extensively developed,” which is equally true for most, if not all, of the 
remaining genera, the glands extending from the end of the clitellum 
to the anus forming a continuous layer underneath the sub-dermal 
muscle layer. The glands are formed of spherical cells elongated in 
Fig. 3. Platybdella anarrhichae. A cocoon gland cell very much magnified, n. nucleus; 
v 1 . nucleoli; <jr. stainable granules in the cytoplasm; 8. a hollow part of the cell 
full of collected secretion; eff.d. efferent duct; s.g. clear granules afterwards found 
in the secretion. 
the direction of the body length; these cells are always large and may 
attain colossal dimensions. In Abranchus brunneus Johansson has 
measured cells up to 250 p. by 100-150 fi. They are of about this size in 
Platybdella anarrhichae, Calliobdella lophii, and, according to Johansson, 
in Abranchus microstomas also, while in the remaining species they are 
smaller, namely from 50-100 /a. The clitellar cells include a very large 
nucleus, usually of irregular form, and provided with numerous nucleoli. 
The nucleus is surrounded by numerous granules which stain as deeply 
with haemalum as does the nucleus itself, and which, previous to the 
18—2 
