508 Transactions.— Miscellaneous. 
cæca as sea-trout. Neither is there evidence that the superabundance of 
food here has resulted in a rise in the average number of ceca during the 
past five years or previously. By referring to my first paper of 1878, it 
will be seen that the mean number for all the trout examined, was 48:3 
while now the number is, as above given, for females, 47:8, and for males, 
487. Thus it is plain the normal average number of cæca is neither on 
the increase nor the decrease in our waters, whatever may be said of their 
range varying. Then, as the same variety of fario in England is said to 
have from 88-47 ceca (although the average is not stated, see Dr. Day 
on the Salmonide), it would seem at first sight as if our trout had suddenly 
developed an increased number of these organs, or in other words, had ex- 
“perienced a rise from 42:5 to 48. But the comparison cannot be held to be 
satisfactory unless all the particulars as to age, weight, sex, stream, and 
feeding are also known. And just as the parr marks, scarlet spots, and 
teeth are affected by age, may not the exca be subject to a similar law ? 
Of course it is impossible to tell to a year or two the age of trout taken in a 
wild state; at least I do not know any rule at present that can give us this. 
So in the absence of any better guide, I have taken the weights of the trout 
as the index of their age, and I find this:—Among eight female trout from 
various rivers, in weight from 1lb. to 2}lbs., the ceca ranged from 838- 
55, with a mean of 42:5 in number; and among fourteen female trout, 
from 8lbs. to 10lbs. in weight, the ceca ranged from 44-61, with 
a mean number of 50°5. Now Giinther’s largest trout was 15 inches, 
which at Home means a trout of about the same age as my 24lbs. 
. trout; while the approximate mean number (42°5) of the ceca observed 
by him is exactly the same as the mean here, for trout of the cor- 
responding age. I have not enough examples from males to warrant 
me as yet in saying how the case is with them; but what I have 
just now stated, proves that variation in the number of the ceca may 
be quite as much due to age (the number increasing with age), as to 
change of habitat from England to Otago, with, in our case, great increase 
in the food-supply. And there is another principle which seems to have 
something to do with the number of these organs. The ceca of the trout 
which had 61 were unusually small, not over one inch in length, while those 
of trout having 40 and 46 were large, in the latter ranging from half-an-inch 
to two and a half inches long. If subsequent researches bear me out in 
these facts, then it will be tolerably evident that while their numbers and 
size are exceedingly variable, there probably may be a fixed relation between 
the extent of the absorbing surface of the pylories, and the weight or age of 
the trout itself. 
