446 



SCIENCE 



[N. S. Vol. XXVII. No. 690 



weeks one had no eyes, the other only one. 

 At the time of exposure of the frogs the 

 eggs were probably in the first polar-body 

 stage, the spermatozoa practically ripe. 

 The cytological study of the material has 

 not been completed. 



The Effects of a Centrifugal Force on the 

 Eggs of Cumingia: T. H. Morgan, Co- 

 lumbia University. 



Rapid rotation drives the yolk to one 

 pole of the egg, the nucleoplasm to the 

 opposite. The polar spindle lies in the 

 protoplasm of the middle zone of the egg, 

 and its orientation is little affected by the 

 centrifuging. The polar bodies may be 

 given off at any point of the surface. The 

 cleavage is like that of the normal egg in 

 all respects, even when all the yolk lies in 

 the smaller of the fii-st two cells. This 

 shows that the determinate type of cleav- 

 age is not affected by' the distribution of 

 the yolk, nucleoplasm or pigment, or by 

 the stratification. In this last respect the 

 results are different from those in the cen- 

 trifuged eggs of the sea urchin, because, 

 while in Cumingia the position of the 

 nuclear spindle is not changed by the 

 centrifuging, in the sea urchin the female 

 pronucleus is driven into the axis of strati- 

 fication. In general, a resting nucleus may 

 be forced to the lighter pole of the cell, 

 owing to the presence in the nucleus of 

 nuclear sap, but the chromosomes and the 

 spindle are more difficult to move, since 

 they have nearly the same specific gravity 

 as the cytoplasm. When they move they 

 do so as a whole, which shows that the 

 spindle figure when present is a definite 

 structure. Embryos develop from the 

 stratified eggs of Cumingia, but whether 

 normal embryos develop for all possible 

 distributions of the different materials of 

 the egg has not as yet been positively de- 

 termined. 



Degeneration in its Relation to Classifica- 

 tion: Charles B. Wilson. 

 On examining the writings of those in- 

 vestigators who have dealt with the group 

 of copepods it is found that nearly every 

 part of the copepod's body has been used 

 by one or another as a basis of classifica- 

 tion. There are nearly as many different 

 schemes of classification as there are au- 

 thors. Is there anything, aside from the 

 inherent excellence of the writings them- 

 selves, which will assist us in deciding 

 their scientific merit? Can we say that 

 any one of the schemes is more rational and 

 logical than the others? 



In endeavoring to answer this question 

 it seems to me that we must take into 

 account first of all the fact that consider- 

 ably more than half of the group live as 

 parasites or semi-parasites on other ani- 

 mals. One of the most common results of 

 parasitism is degeneration, in consequence 

 of which an organ loses its function, then 

 its size and shape, and finally may 

 entirely disappear. No one questions for 

 a moment the influence which development 

 should have upon classification ; any scheme 

 which left development out of considera- 

 tion would be branded at once as worth- 

 less. Why should not degeneration, which 

 is the reversal of development, prove of 

 equal value, especially in a group where 

 it is so finely illustrated as in the copepods ? 

 There are several things which strongly 

 recommend it. It proceeds even more 

 slowly than development, so that we are 

 enabled to follow every step in the process, 

 and almost never need be at a loss. In 

 development it often happens that several 

 new organs appear at a single moult about 

 equally advanced, and it is very difficult to 

 decide which are of the greatest value from 

 a systematic point of view. The newly 

 hatched nauplius has three pairs of ap- 

 pendages, the first and second antennae and 



