532 NATURAL HISTORY OF AQUATIC ANIMALS. 



unimpregnated eggs, having, respectively, thirty five, thirty, eighteen, nine, and seven eggs in a 

 cell; and although, in consequence of the accidental loosening of the wax, and the entrance of a 

 little bubble of air, the duration of the contractions was not in all cases inversely as the number 

 of ova in the cells, yet the general result was rhythmic contraction, and the pseudo cleavage con- 

 tinued longer in the cells containing the smaller number of ova, the eggs which lay nearest to the 

 air-bubble always being the last to cease to move ; the accidental failure of the luting affording 

 thus additional evidence of the importance of oxygen. In all the cells the contraction ceased in 

 from twenty -three to thirty hours, or one-fourth of the time they continued in aerated water and 

 unlimited space. Five similar observations were made on impregnated eggs, with forty-eight, 

 thirty-eight, seventeen, ten, and seven eggs in each cell, with similar but more marked results; 

 the yelk contractions ceasing earlier than in the unimpregnated ova. The cleavage was more 

 rapidly checked than the pseudo cleavage, and still more so than the yelk contractions. Seven 

 experiments were then made to ascertain the relative dependence upon the presence of oxygen of 

 the movements which result in cell multiplication and differentiation, and of the muscular contrac- 

 tions of the embryo compared with the yelk contractions. Two healthy developing ova were 

 sealed in similar cells at seventy-six, one hundred and one, one hundred and twenty-seven, one 

 hundred and fifty, and one hundred and seventy-four hours each, after impregnation, and two free 

 embryos at twenty-four and forty -eight hours after batching. Although the proportion of active 

 organic matter to the medium was so very much less than in the previous experiments with recently 

 impregnated eggs, yet the process of development ceased in all in about seven hours, and the yelk 

 contractions did not continue more than eighteen hours. The movements of the heart continued 

 about the same time, those of the trunk ceasing before the heart. The embryos in the lafoT stages 

 of development more quickly ceased to move than those in the earlier. The inference is, I think, 

 not to be resisted, that oxygen in the surrounding medium is an essential condition of the exercise 

 of the property of rhythmic contractility possessed by the food yelk, as well as of the fissile con- 

 tractility of the formative yelk.' 



"Though Dr. Hansom admits that the quantity of oxygen consumed in these movements 

 appears to be very minute, yet it indicates that a large quantity of eggs, confined, in a small, 

 air-tight space, would consume the oxygen to an injurious extent, during a long journey, 

 and sufficient ventilation is to be considered as one of the necessities in packing eggs for 

 transportation. The sawdust that filled the space around the inner can, in the California 

 shipment, was crowded down with a piece of board, and may have, in consequence, rendered the 

 package more completely air-tight than in the shipments referred to similarly packed. A later 

 .shipment arrived in most excellent condition. The cups in the cases were made four by four 

 inches square, by two deep, with no packing between the cans, and the eggs packed in moss. 

 The most ample ventilation was provided for in the egg-cases. The oxygen given off by live moss 

 is probably the principal reason for its special adaptation in packing eggs for shipment. 



" Dr. Ransom's experiments on the effect of heat have also a practical value in the treatment 

 offish ova, both in transportation and in the troughs. He says: 'Some eggs on the stage of active 

 contraction were cooled until the thermometer placed on the cell stood at 32 F. They all became 

 still, and their yelks globular. They were not frozen ; and I do not doubt that their temperature 

 was higher than that indicated by the thermometer.' The contractions were afterwards restored 

 by a weak galvanic current. In another observation, ' I froze the water in which the eggs were 

 placed, so that some of them were completely, and others incompletely, frozen. The frozen eggs 

 were all more or less opaque, and had their inner sacs ruptured and emptied of yelk in various 

 ^. and their formative yelks tabulated jnid darkly granular. Those which were least frozen 



