OTHER THEORIES OF SPECIES-FORMING. 3S 



in each lot arrives at the spinning time, this proportion being taken 

 to represent the typical condition for the lot. The order in which 

 the lots are arranged in this column corresponds in a general way 

 with that prevalent for the weights at spinning time, and the 

 generalisations indulged in there may, with few exceptions, be 

 applied here. The lots which were well fed during the 1903 

 generation are ahead of all of those given short rations in 1903, 

 whatever ancestry they may have had. Lot I leads here as in the 

 matter of weight. Lots 3 and 5 tie for second place, having held 

 second and third places in weight. Lots 2 and 4 stand in the 

 same relation to one another that they held as to weight. Con- 

 trary to the weight relation, lot 6 follows lot 2 at the spinning a 

 fact which illustrates again the general rule that two generations, 

 of famine are more disastrous than one, but does not lend support 

 to the notion of natural selection on a food scarcity basis as pre- 

 viously suggested. Lot 8, which has had no relief from famine 

 during the entire three years, brings up the rear at the spinning, 

 as might be expected. 



"This check upon functional activity exercised by diminished nour- 

 ishment affects the moulting, the time for the commencement of 

 spinning, and the issuing time for the adults, but the time spent 

 in the spinning of the cocoon, from its beginnings in the threads, 

 of the supporting net to its apparent completion when the cocoon 

 becomes opaque, is practically identical for under-fed and well- 

 fed individuals. A reason for this exception to the tardy habits 

 of the under-fed is to be found in the fact that the under-fed 

 larvae produce less silk (less in size, thickness, and weight) than the 

 well-fed, thus accomplishing more meager results in the same 

 amount of time. That the individuals sentenced to short rations 

 should produce less silk than their well-fed neighbours is certainly 

 to be expected, silk not being made without leaves any more 

 readily than bricks without straw. 



"Not only do short rations protract the time appointed for the 

 spinning, moulting, etc., but they appear to have a more striking 

 effect upon the actual occurrence of the moulting. The normal 

 number of moults for the silkworm larva is four. Five moults 

 have occurred for most of the individuals belonging to the under- 

 fed lots of 1902 and 1903, whereas none of the well-fed individuals 

 has undergone a fifth moult. It would seem, therefore, that the 

 occurrence of a fifth moult may be fairly ascribed to a reduction of 

 food; at least a fifth moult very frequently accompanies it and has 

 suggested the possibility that the enforced fasting of the under- 

 fed larva in the intervals between meals may have the same 

 physiological effect as the normal fasting which precedes the normal 



