
No. 426.] MNWEMERTEAN PARASITES OF CRABS. 44I 
length of the body, usually forming a distinct layer internal to 
the muscular walls of the body, and often thicker than all the 
other layers of the body wall combined. 
Body musculature consists of a thin, oblique or circular mus- 
cular layer and a somewhat thicker, but yet weak, longitudinal 
layer internal to the former. 
Brain and lateral nerves as in other metanemerteans. 
Usually oviparous, though fertilization often takes place 
internally, and sometimes a portion of the ova of an individual 

Fic. 4.— Carcinonemertes epialti. Horizontal section of proboscis in its natural position, 
showing the posterior chamber lying at right angles to the general axis of the proboscis. 
Reference letters as in Fig.3. x 300 
may be retained in the body until the development of free- 
swimming embryos. Development without complicated meta- 
morphosis, although the layer of ciliated cells originally covering 
the embryo is shed as development proceeds. 
Carcinonemertes carcinophila (Kölliker). 
Body slender, commonly 6-15 mm. long when found on gills, 
20-70 mm. long when sexually mature; color yellowish orange, 
