No. 528] SPAWN AND LARVA OF AM BT STOMA 735 



the manner in which they are frequently to be found at- 

 tached in succession to long slender twigs, each mass 

 being usually in contact with its neighbors. A sentence 

 in one paper on A. punctatum (Wright, 1908), "one 

 stem — had within a length of one and a half feet 14 

 bunches of eggs, 15-20 eggs to the bunch," reads very 

 much like a description of spawn of A. jeffersonianum. 

 Many stems so laden have been found each year in the 

 special pools mentioned. The largest piece in Fig. 1 is 

 a portion of one of them. The twigs selected by A. jef- 

 fersonianum are, as a rule, very slender. A. punctatum 

 will make use of both stout and slender twigs indiffer- 

 ently, and no small quantity has been found attached to 

 the margins of leaves and to grass, even in the presence 

 of such twigs as are generally preferred. Eggs of A. 

 jeffersonianum have not been found except attached to 

 twigs or stems of water plants. 



The low vitality of much of the spawn of A. jefferson- 

 ianum is a feature that has been noticed in each year. 

 No accurate estimate of the proportion that dies has 

 been made, but judged roughly by the conditions found 

 in the pools it is probably not overstating the loss to say 

 that three fourths of the eggs do not live to begin gastru- 

 lation. The same proportion of loss has occurred in 

 spawn reared in the laboratory, while spawn of A. punc- 

 tatum brought from the same pools a little later and 

 kept under the same conditions has suffered practically 

 no loss. The egg does not die, as a whole, but cells here 

 and there precede, the others going on dividing as usual 

 one or more times, only to die at last. The surface view 

 of such an egg when death is complete shows an irregular 

 mingling of minute cells with many others two or three 

 times as great, and at intervals others even up to eight 

 or ten times as great, in diameter. These dead eggs 

 imbibe considerable water, and become very much larger 

 than the living ones and under natural conditions are 

 soon infected by fungi ; but in the laboratory they have 

 been kept for weeks and have remained free from it; 

 showing that death has not been caused by a fungus that 



