Arthur. — On the Brown Trout introduced into Otago. 507 



Neither as yet have I discovered any cases of two or any bones of the verte- 

 bras coalescing or subdividing. Whether young trout have fewer vertebral 

 than older ones, has not been examined into by me, but I suspect it may 

 be so. 



The Pyloric caca situated at the end of the stomach where it forms a 

 second bend in joining the great intestine or gut, appear to possess the 

 functions of assisting in absorbing and assimilating the food from the 

 stomach, and of secreting fat. In external colour they possess a rosy flesh 

 tint, when the trout is in good health and on its natural food, and in form 

 are exactly like miniature sausages. But I recently examined the intestines 

 of a trout taken from a pond, where the trout had been fed largely on 

 curdled milk, and where they were fat, strong, and in good condition, when 

 I found the caeca perfectly white, while the other organs were more or less 

 of the same colour. The interior of the caeca, I have often remarked, con- 

 tains an opaque fluid or juice, of an orange, red, or paler hue as the case 

 may be, and very much the same as is present in the intestine itself ; while 

 the exterior is covered by more or less fat, at times indeed smothered in fat, 

 which is tied and laced in a most intricate and secure fashion to the 

 stomach and caeca by strong fibrous tissues like threads. The fat is whitish 

 in colour. From twenty-one female and seven male trout examined, and 

 which were taken from nine different rivers, a lake, and from Otago Har- 

 bour (two from each of the latter), the number of caeca was found among 

 the females to range from 33-61, the mean number being 47-3 ; while 

 among the males the range was from 37-55, with a mean of 48-7. This 

 shows that while the range in number is great (but among males not so 

 much so as among females, just as with the fins), the mean number does 

 not seem to vary much over the whole, or as between the sexes. But un- 

 doubtedly as a means of distinction between the fario and its nearly related 

 species, a comparison of the above figures with those given in Giinther's 

 "Catalogue of Fishes," will prove to anyone curious on the subject that 

 they are of no use whatever. I except, of course, the Loch Leven trout 

 from this category. 



Ichthyologists say, and with apparent reason, that marine fishes are 

 furnished with more caeca than fresh-water forms as a general rule, because 

 they have a wider field to range over for their food, and are in so doing 

 exposed to more numerous and varied enemies than in fresh waters ; and 

 that this necessitates the rapid digestion of food, and quick locomotion. 

 Applying this rule to such a restricted field as our trout supply— or rather, 

 I should say, applying to our trout for such contribution as their limited 

 circumstances can afford to our knowledge on this point — I cannot find 

 that the theory is supported as yet, our brown trout having nearly as many 



