NINETEENTH ORDINARY MEETING. 273 



In the mid-gut and end-gut the epithelium is ciliated, the size of 

 the cilia differing greatly, sometimes being so delicate as to resemble 

 the exceedingly fine protoplasmic processes of the same cells in 

 higher vertebrates. Epithelial insinkings and tubules, to which one 

 can with difficulty attribute a glandular functiori, are present in 

 large numbers in both sections. The epithelium forming them is 

 ciliated, and contains a number of beaker cells. These tubules ai'e 

 undoubtedly the homologues of the Lieberkiihnian glands in higher 

 vertebrates. 



In Acipenser, tubules are present in the mucous membrane of the 

 spiral valve, which are distinguished from those of the neighboring 

 wall of the intestine, in that they are longer and slenderer than 

 those, the cilia of the cells forming them being shorter and more 

 delicate, while beaker cells are wholly absent, but abundantly present 

 in the tubules of the usual kind. Such structui-es are not veiy 

 numerous, and it may be that a study of fresh material may show 

 them to be not materially different from the others. In this genus 

 also the epithelium of the spiral valve is very strongly ciliated, and 

 its shallow crypts are abundantly supplied with beaker cells. 



One important point in connection with the histology of the 

 spiral valve in Aci2)enser has yet to be noticed. Usually the valve 

 is thick, and a cross section of it shows to what the greater part of 

 this thickness is due : lymph follicles, often over a dozen in number 

 in a single vertical section. Hyrtl described a large lymph organ 

 as forming the greater part of the thickness of the valve in Acipenser 

 ruthenus, and Ayers has found something similar in this species and 

 in Lepidosiren. These follicles in Acipenser ruhicundus are, in all 

 probability, the homologues of Peyer's patches which are therefore, 

 so far as is yet known, confined in fishes to Acipenser and Lepidosiren. 



In Amia the epithelium of the mucous membrane is ciliated from 

 the pharynx to the vent. Cilia are present in the same extent in 

 Acipenser and Lepidosteus, except in the stomach. 



The pyloric appendage in Acipenser and Lepidosteus is lined on its 

 inner surface by epithelium, resembling in every respect that of the 

 mid-gut, and completely lacking a glandular character. These 

 appendages, in some other fishes, have been found to secrete pepsin, 

 trypsin,[and diastase. This is not the case in Acipenser ; no enzymes 

 were found when proper pi-ecautions were taken to remove the 

 mucus and food matter, which usually gains an entrance by the 



