60 



SCIENCE. 



[Vol. I., No. 3. 



will, in the course of time, come to us through 

 the work of successive 'Balfour students.' 



The sum alreadj^ subscribed in England is 

 more than sufficient to provide for the Balfour 

 studentship : but a memorial to such a man 

 and for such objects should be international ; 

 and we are glad to learn that a representative 

 committee of American naturalists, with Mr. 

 Alexander Agassiz at its head, is being organ- 

 ized for the purpose of obtaining subscriptions 

 to the Balfour fund. Few scientific men in this 

 country are in a position to contribute large 

 sums ; but we trust that all American biologists 

 will give something, whether they be investi- 

 gators, teachers, or students. A general sub- 

 scription from naturalists on this side of the 

 Atlantic would be a most graceful testimony 

 to the esteem in which Balfour's character and 

 work are held bj^ us ; and would at the same 

 time express our approval of the idea to make 

 the monument of an eminent scientist not a 

 bronze or marble statue, but a permanent en- 

 dowment for the advancement of knowledge. 



REARING OYSTERS FROM ARTIFICI- 

 ALLY IMPREGNATED EGGS. 



During the past three years the writer has 

 been engaged upon the investigation of this 

 subject, with the view of reaching some prac- 

 tical results which would be available in the 

 hands of 03'ster-culturists. Until last j'ear his 

 eflForts under the auspices of the U.S. fish com- 

 mission had been comparatively fruitless and 

 unsatisfactor3'. In Jul}' and August last, in 

 association with Col. M. McDonald, the ex- 

 perimental work was resumed at St. Jerome's 

 Creek, St. Mary's County, Maryland. Col. 

 McDonald devised a simple combination of 

 glass apparatus, consisting of a series of jars 

 connected together with rubber tubing, some- 

 what in the manner of a series of Wolff's bot- 

 tles, with an open glass aquarium at a higher 

 level as a feeder, or reservoir, while the last 

 jar of the series discharged into a similar cj'- 

 liudrical aquarium standing on the floor. The 

 sea-water introduced into this contrivance was 

 carefully filtered through cotton-wool, to re- 

 move all sediment and foreign organisms. 

 The circulation was maintained in this contriv- 

 ance bj' baling the water from the lower into 

 the upper aquarium ; the water passing contin- 

 ually through the intervening series of jars, 

 which were, in effect, simply enlarged portions 



of the siphon-tube passing from the upper to 

 the lower aquarium. No difficult}' was experi- 

 enced in keeping the water in this apparatus 

 fresh and sweet without renewal. 



On the 23d of July a batch of oyster-eggs 

 was introduced into this apparatus, impregnat- 

 ed b}' a method to be hereafter described. On 

 the 24th, and just about twent3'-four hours after 

 impregnation had taken place, an inspection 

 of the transparent sides of the jars and aqua- 

 ria was made ; and to our great surprise we 

 found immense numbers of embryos with the 

 valves of the larval shell covering the sides of 

 the body, and adherent to the inner surfaces 

 of the glass vessels. In some places upwards 

 of twenty-five might have been counted to the 

 square inch. Every available part of the sur- 

 face of the vessels was, however, more or less 

 afi'ected bj' these affixed embryos. Some of 

 the jars were then taken from the closed circuit, 

 and a continuous current passed through them, 

 which it was found did not dislodge the em- 

 brj'os ; but in two to three days more it was 

 found that most had died or been detached, 

 even in the portion of the apparatus not affect- 

 ed bj' a continuous current of fresh sea-water. 

 The gratifying result which we had anticipat- 

 ed at the beginning of our experiment was, 

 however, not realized, except in so far as it 

 determined that fixation of the embryos took 

 place at an early period under favorable con- 

 ditions, or in about twenty-four hours, and that 

 they might be reared from artifleiallj' fertilized 

 ova. Efforts to repeat our first successful ex- 

 periment failed, owing, probably', to the high 

 temperature then prevailing. 



The next advance made was when the writer 

 hit upon a physical test by means of which the 

 sexes of the spawning adults can be instantly 

 determined bj' the most ignorant person. It 

 was found, that if the ova were squeezed from 

 the ovarj', and dropped into sea-water in a 

 glass dish resting on a dark ground, thej' would 

 break up into a distinctly granular cloud ; while 

 the milt would not so readily break up, but 

 would tend to mix slowly with the water as a 

 milk}' substance, the particles of which were 

 not perceptible to the naked eye, and, if stirred 

 about in the water, would not break up at once, 

 but be drawn out into wisps and streaks 

 resembling in miniature cirrus or mare's-tail 

 clouds. This test was an infallible guide ; so 

 much so, that a pocket-lens was found to be of 

 no advantage, as we had formerly supposed. 

 We also found, that if the eggs did not separate 

 at once, when dropped into the water, they 

 were not so mature as the.y should be. 



Another important improvement was also in- 



