190 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



tlie same authority, is 50 days, temperature of sea-water 31° F. Our 

 own experience at Wood's Holl last winter taught us that the develop- 

 ment of the ova of the cod was capable of being accelerated, for those 

 in a glass cone near a warm stove hatched out in a shorter space of 

 time, IC days, than any others. Our power to accelerate the rate of 

 development of the cod may be of use, as we may thereby be enabled to 

 hatch out a large percentage of ova in a very few days. Whether the 

 young would be as vigorous as those incubated in the natural way re- 

 mains to be learned. 



Acceleration, like retardation of development, is accomplished by in- 

 fluencing the rate of the rhythmical metamorphoses of the nuclei of the 

 cells of the embryo. Accelerate the rate of these metamorphoses and 

 segmentation is hastened so as to cause development to proceed more 

 rai)idly. The stimulus is heat, a mode of motion, and we are forced to 

 believe from what has preceded that the nuclear metamorphoses are 

 simply the si^eciflc modes of motion of the cellular life centers. The 

 molecules of the nuclear spindles, reticuli, «&c., are made to move more 

 or less actively in obedience to the fluctuations in the activity of this ex- 

 ternal stimulus. All this goes without saying, however, that the pro- 

 toplasm, which in the case of every cell invests the nucleus, may not 

 also share in the process ; it is but natural that it should, because free 

 nuclei, independent of any investment of protoplasm, are unknown to 

 histologists. 



Inasmuch as the granular particles of nuclear fibers and reticuli ex- 

 hibit certain modes of motion which appear to be characteristic in the 

 course of segmentation, and since we find that heat, admittedly a mode 

 of motion, accelerates or retards the motion of living nuclear matter in 

 its segmentational metamorphoses, are we not warranted in assuming 

 both of these kinds of motion to be in a degree correlated and interdepen- 

 dent ? The significance of the views here set forth in their bearings upon 

 general physiologj^ and pathology would appear to warrant the belief that 

 we may yet be able to solve some of the knottiest problems in biology. 

 Their practical significance in relation to the problems which have pre- 

 sented themselves for solution to the Fish Commission will also be ap- 

 parent. 



