1884.] 



AMONG THE SALMONIDjE. 



377 



65, in January 18, and in February 4, or a total of 87 deaths, while 

 an additional 199 eggs were found not to have been originally im- 

 pregnated. From the foregoing experiment we can draw the con- 

 clusion that the mortality was only 1 in 46 eggs, when those of 

 mature Lochleven Trout were milted from immature Salmon-parr. 



But although this mortality was only slightly in excess of 2 per 

 cent, of the eggs, such by no means gives a true index to the result 

 of the experiment, for it was soon perceived that the milt of the 

 parr (at least in this instance) was insufficient to satisfactorily im- 

 pregnate the eggs of the Trout, in order to raise a strong and vigorous 

 brood of alevins, while weak ones are useless for stocking pur- 

 poses, even should they overcome the diseases and dangers of their 

 youth. 



On February 15, 1884, some thousands were hatched from these 

 eggs, but nearly all were seen to be suffering from what has been 

 termed dropsy, or blue swelling of the yelk-sac. This non-contagious 

 disease, as observed by Livingston Stone, is one for which no remedy 

 is known, and concerning which he remarks no cause for its origin 

 had been ascertained. Appearances led me to the belief that in this 

 instance such must have been due to insufficient vitality in the 

 young, a consequence of the imperfect fecundating power of the 

 milt. In that such cannot be due to simply crossing tliese two 

 forms, is evident from the 212 examples of hybrids between the male 

 Salmon and female Lochleven Trout, and which are now in the octagon 

 pond at Craigend, as I have observed upon. 



Fig. 1. Salmo levenensis, 29 days old. 



Fig. 2. , 43 days old. 



Pig. 3. fontinalis (J, Salmo levenensis 5 , 27 days old. 



Fig. 4. salar (}, Salmo levenensis $ , 27 days old. 



Fig. 5. , , 41 days old. 



Fig. 6. , , 91 days old. 



March 12, 1884, I first saw these young fish, then almost one 

 month old, and their average length being 0*8 of an inch ; but what at 

 once struck an observer was the large and pyriform umbilical sac, 

 which seemed to anchor them to the bottom of the tank ; some were 

 thus seen singly, others in groups, while every now and then one 

 ■would start up and swim a short distance in an irregular or spas- 

 modic manner, and then subside to the bottom. This dropsical 

 enlargement in a considerable proportion of the fish was 0'35 of an 

 inch in length, and 0'2 of an inch in diameter where it was widest, 

 while it stood out in tolerable relief from the enclosed yellow yelk- 



