508 Transactions. — Miscellaneous, 



crcca as sea-trout. Neither is there evidence that the superabundance of 

 food here has resulted in a rise in the average number of crcca 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*3, and for males, 

 48*7. Thus it is plain the normal average number of caeca 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 38-47 caeca (although the average is not stated, see Dr. Day 

 on the Salmonicke), 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 crcca 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 lib. to 2jlbs., the crcca ranged from 33- 

 55, with a mean of 42-5 in number; and among fourteen female trout, 

 from 31bs. to lOlbs. in weight, the crcca 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 2^1bs. 

 trout ; while the approximate mean number (42-5) of the crcca 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 crcca 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 crcca of the trout 

 which had Gl 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 pylorics, and the weight or age of 

 the trout itself. 



