Artuur.—On the Brown Trout introduced into Otago. 509 
Our heavier still rivers do not appear, with their grand stock of smelts 
and whitebait, etc., to cause any increase in the number of the pyloric ceca, 
over those of trout in our rougher and poorer streams. This I have proved 
from a careful examination of a fair number of specimens. And, it is also 
curious, that a sea-trout caught in Sawyer’s Bay, which I opened, had only 
40 ceca, while it must have had the finest possible range of feeding 
ground. 
What I have now said regarding these organs in our trout amounts to 
this:—The actual number of ceca observed in Otago is greater than 
Giinther’s recorded number of them at Home; but the evidence I have 
adduced shows that this increase in number is not owing to an additional 
demand on the ceca to work, necessitated by the presence of more food, 
but in all probability to a difference in age of the fish examined. Or, more 
plainly, there has really been no alteration in the number of the pyloric 
ceca, or in the extent of their absorbing surface. 
There remain but one or two observations which I have to make on 
structure before finishing my paper, which has expanded into dimensions I 
did not anticipate, so much so that I may have to reduce the appendix I 
thought of, if I do not omit it altogether. The first is, that in nearly every 
female with developed ovaries the left lobe is much longer ‘than the right 
lobe. And, as to the theory of the thickness of coating in stomachs of 
trout, (as the Gillaroo trout of Ireland), being a consequence of the food 
being shellfish, this I must say—that most of our rivers contain a wonderful 
number of the previously mentioned Limnaa, an active little mollusc, which 
I have found in our trouts’ stomachs in incredible numbers. At the same 
time there are parts of some rivers where they are absent, and where of 
course the trout cannot get them to eat. I have not paid particular 
attention to the action of any food on trouts’ stomachs as yet; at the 
same time, had there been any difference between those of trout from 
either feeding grounds, it is probable that I should have noticed it. And, 
I certainly have not seen either a thickening or hardening of the walls of 
the stomach.* 
Remarks on Zion: 
1. The first variation is a decided one in the spawning season, being 
two months later, and the duration of hatching a fortnight longer, than in 
England. But what may be the cause of this I cannot explain. 
* Since writing above, I have found this shellfish at the head of the stomach, and 
near the vent in great intestine of a one-pound trout from Waipahi River, and in both 
cases the living animal was digested out of the shells, while these were not broken or 
affected in any other way. 
