458 SCHULTE, SET WHALE. 



was very delicate and gave away when the attempt was made to straighten it out, so that its 

 extent could not be ascertained. It seemed of moderate size, but I do not think it would have 

 reached to the umbilicus. 



The retrogastric space is invaginated from above by the processus papillaris, which com- 

 pletely fills the oval between the stomach and the pancreas extending caudad as far as the colon. 

 The cavity has then something of the shape of an oval dish with its marge applied to the peri- 

 phery of the papillary process. Here the reflection of its peritoneum takes place, ventrad and 

 to the left as the ental layer of the gastro-hepatic omentum to the lesser curvature and thence 

 over the dorsal surface of the stomach into the omentum; to the right and dorsad upon the 

 transverse pancreas and then into the dorsal wall of the omentum. From a comparison of the 

 line of reflection at the papillary process and that of the great omentum, it is seen that the retro- 

 gastric space broadens markedly caudad. I could not find an extension of the lesser sac upon 

 the right of the oesophagus corresponding to the isolated cavity here present in Tursiops, nor 

 could I ascertain that it reached the dorsal paries at any point. 



In the whales it is evident that very peculiar relations obtain in the topography of the 

 upper abdomen and in the disposition of its peritoneum. Hunter first described the obliteration 

 of the foramen of Winslow. "In some of this tribe there is the usual passage behind the vessels 

 going to the liver, common to all quadrupeds I am acquainted with; but in others, as the small 

 Bottle-nose, there is no such passage, which by the cavity becomes a circumscribed cavity." 

 He does not specify further the forms in which the foramen persists, nor have I in the literature 

 as yet come upon another reference to this condition. It is evident however that members 

 of both suborders concur in this obliteration, and in Tursiops truncatus, of which I had the 

 opportunity at the New York Aquarium to examine three specimens, there is also reduction of 

 the lesser sac in the loss of the splenic and the all but complete obliteration of the Spigelian recess. 

 Taken in conjunction with the wide differences between the suborders in the infracolic com- 

 partment as pointed out by Weber this resemblance is of some theoretic interest. For under 

 conditions which are sufficient to produce in both the highly peculiar, and probably unique, 

 modifications of the lesser sac, the divergent evolution of the lower digestive tract is evidence of 

 the plasticity of the alimentary canal, and its potentiality of highly diverse modification 

 within the limits of a single order. The major peculiarity is undoubtedly the reduction of the 

 lesser sac, and may find its determining factors in the crowding of the upper abdomen by the 

 huge liver and stomach under pressure from without, even though the extreme forward displace- 

 ment of the intestine of the Balsenoptera foetus is not present in a somewhat larger foetus of 

 Tursiops, which has been examined for this point. Here however the relatively enormous liver, 

 with its massive left lobe, had effected even a greater degree of crowding of the viscera in the 

 upper abdomen, although the intestine was largely postumbilical in position. The primary 

 condition, operative with differing details in both, would seem to be the torpedo-form of the 

 body, with its major girth located in the preumbilical region. 



