144 BULLETIN OF THE BUREAU OF FISHERIES. 



The recurrent intestine is either round or elliptical in cross section at its posterior end. 

 As it runs forward one side becomes flattened and develops a high columnar, ciliated 

 epithelium which is parted in the middle by a longitudinal furrow (fig. 126, opp. p. 143). 

 The walls which are continuous on either side with this thickened portion are composed 

 of comparatively low epithelial cells, but as they pass around to the opposite side of the 

 intestinal wall they become progressively higher, although they do not reach the height 

 of those on the fiat side. Between the epithelial cells there are scattered a few tall 

 mucous cells. The epithelium is bounded externally with a basal membrane which is 

 thickest on the side where the epithelial cells are highest. External to it there is a thin 

 layer of circularly running fibers. 



The terminal intestine is a continuation of the recurrent intestine and preserves the 

 same semicircular outline of the latter with the very tall epithelium lining the flat side. 

 The furrow, however, which divides this thickened portion into right and left halves is 

 much deeper than that in the recurrent intestine, and the ciliated cells gradually become 

 much lower (fig. 127, opp. p. 143). Mucous cells are distributed in considerable numbers 

 between the epithelial cells. The basal membrane on which the ciliated cells rest is 

 well developed and covered externally with a thin layer of circular muscle fibers. 



The crystalline style as observed by Haseloff (1888) and List (1902) is composed of a 

 somewhat firm, elastic substance of gelatinous consistency. In the fresh state it is 

 perfectly clear and transparent. In cross section it shows a series of concentric layers, 

 the central portion presenting a homogeneous structure, while that near the periphery 

 is granular in appearance. According to List (1902) the crystalline style is formed 

 from secretions produced by the high epithelial cells, in the side walls of the direct 

 intestine. The secretion consists of granules which are molded into the surface of the 

 crystalline style. 



The liver occupies the anterior part of the visceral mass and completely surrounds the 

 stomach and those portions of the intestine which lie anterior to the heart. The larger 

 portion of the liver occupies the right side of the body. The organ is single and composed 

 of numerous lobules which in turn are made up of elongated glandular acini. The 

 discharging canals unite successively with the main canals which empty into the stomach 

 by large openings that often cause irregularities in the walls. The number of main 

 canals appears to vary between 8 and 15. 



List (1902) says in regard to their structure that the main canals to the stomach 

 are unevenly ciliated throughout, the epithelium being composed of two distinctly 

 different elements of which each circles one-half of the canal when seen in cross section. 

 On one side the columnar cells are lower and broader than those of the opposite side and 

 contain numerous granules lying in their distal ends; the nuclei are large, each one con- 

 taining a conspicuous necleolus. Cilia are absent. The epithelium lining the opposite 

 side of the canal is composed of high columnar cells which bear long cilia arising from 

 distinct basal bodies; the nuclei are small and contain numerous chromatin granules 

 with or sometimes without a nucleolus. Externally the canal is surrounded by a well- 

 developed layer of circular muscles (fig. 129). 



The epithelium of the secondary liver canals is continuous with that of the main 

 canals and differs from it in having a lining of broad, low columnar cells that contain 

 large nuclei with a conspicuous nucleolus (fig. 1 30) . The protoplasmic portion is further 



