770 REPOKT OF COMMISSIONER OF FISH AND FISHERIES. [8] 



ment, besides numerous hypotrichous infusoriaus. These are not charge- 

 able with killing the embryos, but probably appropriate their dead 

 bodies after they have fallen to the bottom and begun to disintegrate. 

 Temperature of water ranged from 84° F. to 86° to-day. 



July 22. — The remarkable set of experiments in the incubation of the 

 ova of the oyster instituted to-day by Colonel McDonald led to a new 

 series of experimental results as singular as they are contradictory. 

 The above-named gentleman with characteristic ingenuity arranged a 

 series of his hatching-jars so as to form what he called a closed circuit. 

 The first element of the apparatus was a cylindrical glass aquarium, 

 about 14 inches in height, placed about 4 feet above the level of the floor 

 of the hatching-house. This was connected by means of a siphon tube 

 of rubber to one of his glass hatching-jars, such as are used in hatching 

 shad ova ; a glass tube passing through the cork formed the inlet con- 

 nection, and a similar tube reaching nearly to the bottom of the jar was 

 joined to a rubber tube outside to form the outlet. Then followed a 

 second jar connected to the first, with similar pipe connections, except 

 that it discharged into a glass aquarium set at a still lower level, the 

 bottom of which was covered with pebbles, to which some living sea- 

 weeds were attached and in growing condition. The water then passed 

 through a rubber siphon tube from this second aquarium to two more 

 closed hatching-jars placed at a lower level and arranged just as the first 

 pair; the discharge-pipe of the last jar then carried the water into an 

 aquarium, which rested on the floor. In order to maintain a circulation 

 in this apparatus it was necessary to keep dipping up the water very 

 carefully, so as not to injure the embryos, from the aquarium resting on 

 the floor into the one standing 4 feet above that level. In order to sup- 

 ply lime to the embryos the two pairs of closed hatching-jars had been 

 about one-third filled with clean sun-bleached oyster shells, and the pur- 

 pose to be served by the living Laminarice placed in the middle aquarium 

 was to supply oxygen to the embryos and absorb the carbonic diox- 

 ide thrown off by these and other organisms in the jars and aquaria. 

 The water with which the apparatus was charged was carefully filtered 

 through a cotton-wool filter so as to free it from sediment and objection- 

 able organic matter. After the apparatus was filled no attempt was 

 made to change the water, as it was soon discovered that the water 

 would remain perfectly sweet without renewal. Theoretically, this con- 

 trivance appeared to satisfy all the conditions of the problem which 

 had been placed before us for solution. 



A lot of eggs were placed in this contrivance at 11 a. m. I was par- 

 ticular to get as fine a lot of ova as possible, so as to test the matter 

 fairly. In order to do this the eggs were expressed from the adults by 

 the new method already alluded to, and fertilized so successfully that 

 I am convinced fully ninety per centum were developing normally when 

 put into the apparatus. My delight and astonishment the next morn- 

 ing at finding that many of the embryos had apparently attached them- 



