40S Bdshford Dean Memorial Volume 



THE W^VTJLAR INTESTINE 



In my three specimens the vahnilar portion of the digestive rube is spindle'shaped, 

 but tapers much more rapidly in its caudal half; the cephaUc end is almost truncate. 

 Gunther"s (1887) figure (my Figure 15, plate IV) gives proportions similar to those found 

 in my specimens save that in his dissection the \'aI\Tjlar intestine is laid widely open 

 after being sHt longitudinally. In my specimens the external surface of the valvular 

 intestine is either bluish-gray or brown, appearing much darker than the other portions 

 of the digestive tube. The ^.-alls are ver}' thick, ranging from 5 or 6 mm. near the cephaHc 

 end, to 1 or 2 mm . at the caudal end where it joins the colon. In two of these speci- 

 mens the spiral valve extends to the extreme cephalic end of the thick-walled portion 

 of the digestive tube, but in Xo. II the spiral valve stops at about 20 mm. from the ceph- 

 alic end of the thick-v.-^Ued portion. For the remaining distance the inner surface 

 shows \-Lllo5ities similar to, but larger than, those found in the region of the spiral valve. 

 On this account, and also because of the thickness of its u-alls, this part is assigned to the 

 \^h"ular intestine. For similar reasons I have included v.'ith the \^l\njlar intestine a short 

 thick-walled portion, with a velvety lining, between the caudal end of the spiral valve 

 and the thin-walled colon. In specimens I and III the length of this region is 15 mm. ; 

 in Xo. II it is 20 mm. The posterior four-fifths of the vahnilar intestine lacks a mesentery. 



In my specimen Xo. I, the form of the \'ahnalar intestine seems perfectly preserved. 

 The maximum diameter is only 26 mm., while the length is 190 mm. In Xo. II the val- 

 \Tjlar intestine is much larger; its maximum diameter is about 33 mm., while its length 

 is 240 mm. In Xo. Ill the organ is about the same size as in Xo. II, but is so irregularly 

 molded that its diameter cannot be accurately measured. 



In Chlamydoselachus the spiral \'alve is a continuous ribbon-Hke structure attached 

 by one edge to the inside of the wall of the intestine, while the other edge is either free, 

 ■^^-inding about a central ca\rity, or is attached to an axial strand. In specimen Xo. I 

 the anterior third of the spiral valve has a central cavity large enough to admit a pencil; 

 the posterior third has a much smaller central cavity, while the middle third has an axial 

 strand. In specimen Xo. II a central cavity alternates with an axial strand at irregular 

 intervals. In specimen Xo. Ill there is a central ca\'ity of moderate size extending the 

 entire length of the spiral \^lve except in its middle portion, where there is a short axial 

 strand. In the specimen portrayed by Giinther (my Figure 15, plate IV) it is clear that 

 there is a central cavity in the caudal half and at the cephaHc end, while the interval 

 between has possibly an axial strand. 



In its natural position, the spiral valve of Chlamydoselachus does not He vertical 

 to the waU of the intestine; it slants either forward or backv.^rd. Thus each coil has the 

 form of an asymmetrical cone, of which the apex may be missing. \\%en the intestine 

 is contracted, the spiral \^lve makes an acute angle with the wa.]l of the intestine; when 

 it is expanded, the spiral valve may be drav^-n into a nearly transverse position. 



