178 BULLETIN OF THE BUREAU OF FISHERIES. 



This layer extends without change or interruption over the inner ends of the pore canals, 

 showing that the latter are not to be regarded as ducts, each connecting with a specific 

 glandular body, but rather the entire inner layer is probably glandular and shares all 

 the pore canals in common. This view is strengthened by the presence, inside the 

 hypodermis and firmly adherent to it, of the second soft layer, several times as thick, 

 indistinctly separated into cells, and containing a coarse protoplasmic network with 

 numerous irregularly disposed nuclei, sometimes single and sometimes gathered into 

 bunches {il, fig. 8, pi. vu). 



This layer has all the characters of glandular tissue and varies considerably in 

 thickness, being thickest where the pore canals are most numerous, especially at the 

 pregenital prominence. (See fig. 13, pi. vii.) 



Here the cells are much more distinct, in fact they are usually entirely separated 

 one from another, and each is multinucleated. 



This layer is entirely lacking in the head, the arms, and the appendages, or just 

 the places where the pore canals are fewest in number. 



The digestive canal.— The mouth opens directly into the oesophagus, which is 

 cylindrical and short, and extends diagonally downward to the stomach, from which 

 it is separated by a powerful sphincter muscle. 



The walls of the oesophagus (oe, fig. 7, pi. vu) are tolerably thick and are connected 

 with the dorsal and ventral walls of the head and with the stomach walls by powerful 

 muscles (m), which must be capable of widening the lumen of the oesophagus and thus 

 producing a suction through the mouth. Such a widening would produce the so-called 

 "crop" described and figured by Hartmann in barnimii, which thus becomes a temporary 

 condition of the gullet rather than a permanent portion of the digestive apparatus. 

 Between the horns the stomach widens and sends out a lateral lobe on either side toward 

 the bases of the horns but not actually reaching them. It then narrows and passes 

 insensibly into the intestine, whose anterior portion is often thrown into numerous con- 

 volutions (fig. 9, pi. vii), and which maintains a wide lumen throughout the entire body. 

 At the pregenital prominence the intestine is abruptly narrowed into the rectum, which 

 is spindle shaped, widened through the center, and very narrow and slitlike at the pos- 

 terior end (re, fig. 10, pi. vii). 



The wall of the stomach-intestine is made up of an outer muscular layer and an 

 inner epithelium, and the latter has the same structure as in other parasitic copepods, 

 larger digestive cells being interspersed among the epithelial cells. (See fig. 62, pi. xiii.) 

 But there are also in the epithelium of the stomach and one or two of the anterior convo- 

 lutions of the intestine numerous scattered cell bodies, which are totally unlike anything 

 found in the other families of copepods. They are spherical in shape and possess a com- 

 paratively large and very distinct nucleus and nucleolus. 



The body of the cell outside the nucleus is filled with small granules, sometimes 

 colored greenish or brownish, mixed with which are larger colorless refractive bodies. 

 These may be spherical, angular, boat-shaped, buckle-shaped with a crossbar through 

 the center, or simply irregular and strongly granulated. Hartmann suggested that these 

 might be psorosperm, whose existence in the epithelial cells of the intestine was abun- 

 dantly proved by Leuckart, Wagener, and Reincke. 



Considering that these parasites burrow into the tissues of fish and feed upon the 

 blood and juices found there, it would be strange if they did not obtain some psorosperm. 



The transverse muscles of the walls of the intestine and rectum are comparatively 

 powerful and produce a strong peristaltic movement. This is the principal factor caus- 



