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vered with a dark deposit, from the impure condition of the water, 

 and large numbers of the ova died daily in consequence. Another 

 batch of filters was then fixed, and a fresh supply of filtered water 

 obtained ; and no more sediment was deposited upon the ova. Not- 

 withstanding this, they continued to die for some days ; but about 

 the 20th, the whole of the deposit, which had settled upon the bottom 

 of the boxes and upon the ova, began to rise towards the surface in 

 the form of Confervse ; the bottom of the boxes and the remaining 

 ova appeared quite fresh and clean ; the surviving ova rapidly 

 assumed the perfect state of the young fish ; and on March 7th the 

 young fry began to move about (the outer covering being thrown off), 

 endeavouring to hide themselves between the stones and gravel. The 

 temperature of the water during this experiment was 57°. In order 

 to ascertain if any advantage could be gained by placing some of 

 these in filtered water at a lower temperature, a number of them 

 were carefully removed to a glass tank, supplied with a fountain at 

 the temperature of 54°. In this they appeared to be doing well, 

 were evidently larger and more active, and exhibited great promise. 

 Unfortunately, on the morning of the 13th, the workmen having 

 been ordered to make some alteration in the water pipes in the build- 

 ing, turned off the water, leaving the young salmon, together with 

 the ova which had not yet been hatched, five or six hours without 

 fresh water, in the tropical end of the building : in consequence of 

 this, they were all destroyed, and this interesting experiment delayed 

 for a whole year, as it is impossible to obtain the ova until the next 

 breeding-season. 



There are, however, some important facts learned from this expe- 

 riment, one of which is the early period of hatching. Previous ex- 

 periments have shown that 60 days usually expire before the young 

 come to life; sometimes 140 days have passed. This experiment 

 has proved that the young fish can be hatched in 30 days : it yet 

 remains to be tested whether this is an advantage. It is certain 

 that in the case of more highly organized and warm-blooded animals, 

 their production at an earlier period than the ordinary one is at- 

 tended, if not with death, at least with great debility ; while, on the 

 other hand, it is not possible to retard the operations of nature beyond 

 the ordinary period without destroying the mother or the offspring. 

 There are many circumstances that induce the belief that the young 

 fish would be stronger by the early development ; but no positive 

 conclusion can be arrived at without further experiments. 



Mr. Gould took occasion to lay upon the table specimens of all 

 the known species of the genus Elanus, and made some observations 

 upon their habits and economy, and their distribution over the face 

 of the globe. With the exception of Elanus leucurus, which is 

 confined to America, all the other species of the genus are inhabit- 

 ants of the Old World, the Elanus melanopterus being found spa- 

 ringly in Southern Europe, Africa, the Indian Peninsula, and pro- 



