NOVEMBEE 28, 1913] 



SCIENCE 



787 



apparently overlooked by Mitchell, below in 

 anotber connection. 



If my interpretation of physiological rhythm 

 be correct, as outlined in the preceding para- 

 graph, nutrition and male production stand in 

 the relation, not of cause and effect, but of two 

 eilects of some cause. If this interpretation is 

 correct, high nutrition and male production 

 are not inseparable; and there is evidence that 

 they are separable. Early in my work on 

 Hydatina I noticed that periods of abundant 

 male production were also periods of rapid 

 growth (the fact which Mitchell emphasizes 

 for Asplanchna) , and I was almost convinced 

 that anything which increased metabolism 

 would also increase the proportion of male- 

 producers.^ But in healthy lines I later found 

 that long periods were passed through in 

 which the rate of growth and reproduction was 

 very rapid, yet not a single male-producer ap- 

 peared. In one instance, there were twelve 

 successive generations in which no family com- 

 prised less than 46 daughters, some of them 

 over fifty, which is almost the maximum of all 

 my records. At the same time the females laid 

 16 to 22 eggs per day, depending on tempera- 

 ture, quite as rapidly as in the waves in which 

 I had previously noted large numbers of male- 

 producers. Yet not one male-producer ap- 

 peared in these twelve generations. Hence, 

 when actual counts were made from numerous 

 families, for the purpose of proving that rapid 

 metabolism and male production were inter- 

 dependent, that thesis could not be established. 

 While periods of many male-producers were 

 on the whole periods of rapid metabolism, not 

 every period of rapid metabolism was a period 

 of many male-producers. Kapid metabolism 

 could occur without abundant male production. 

 One is driven, it seems to me, to the conclu- 

 sion that when male production and rapid 

 assimilation (" nutrition ") occur simultane- 

 ously, both are probably effects of one cause; 



I So nearly convinced was I that this relation 

 existed, that I expressed the idea before a public 

 gathering at the laboratory of the Brooklyn Insti- 

 tute of Arts and Sciences at Cold Spring Harbor, 

 in the summer of 1909, but never in any pub- 

 lished work. 



but that rapid assimilation may have other 

 causes which do not at the same time cause 

 abundant male production. 



Mitchell does not, however, rely wholly upon 

 the high nutrition which accompanies physio- 

 logical rhythm to explain male production. 

 The " nutrition " which depends upon the 

 available supply of food is also held account- 

 able; for the author conducts experiments in 

 which the food supply is altered, and obtains 

 what he believes to be positive results thereby. 

 The general conclusion from these nutrition 

 experiments is that " male production follows 

 upon the summation of favorable external and 

 internal conditions, plus a sudden interruption 

 by a nutritive check." This check is starva- 

 tion. The experiments, however, appear to me, 

 for reasons about to be stated, quite inade- 

 quate. For example, one experiment consisted 

 in isolating females from periods of rapid 

 metabolism and from periods of depression, 

 starving their offspring for a period after 

 birth, and noting whether the daughters were 

 male- or female-producers. Each part of this 

 experiment involved only about ten individ- 

 uals. Notwithstanding great irregularities in 

 the occurrence of male-producers, irregularities 

 which the author admits sufficiently to explain 

 certain exceptions, the ten individuals are con- 

 sidered valid evidence. The apparent lawless- 

 ness 'of the occurrence of male-producers is 

 sometimes astonishing. In Hydatina, in an 

 extreme case, two sisters, the fourth and fifth, 

 respectively, in their family, reared under 

 what were aimed to be identical conditions, 

 each produced a family of over forty. One 

 family comprised over fifty per cent, of male- 

 producers, the other none at all. In view of 

 such irregularities, experiments including less 

 than eight or ten generations have in my work 

 been regarded with suspicion, unless the effects 

 were quite marked. If such irregularities in 

 the occurrence of male-producers are found in 

 Asplanchna, ten individuals do not form a 

 basis for conclusions. 



Furthermore, it is questionable whether 

 starvation can have such an effect on the indi- 

 vidual starved as to change a female-producer 

 to a male-producer. I have shown for Hyda- 



