THE EMBRYOLOGY OF EUVANESSA ANTIOPA. 99 



a food-gatlierinp^ mania that it had at last itself fallen victim to its own 

 devices. Is the nucleus merely j)as8ive in this respect? Then it grew 

 with the cell's prosperity till it had reached a point where its organization 

 was not enough to hold it together. 



The egg, after the disappearance of the nucleus, is no longer a cell in 

 the sense it was before : it has not the organization of a cell ; it is the re- 

 mains of what was a coll. It is a mass of yolk surrounded and imbedded in 

 live protoplasm. But this protoplasm exhibits no harmonious action for 

 the accomplishment of one end ; it lacks the interrelations necessarv to a 

 unit like a cell. Its history shows more fully the truth of this conclusion. 

 The earliest stages of its future development are unknown, but as in other 

 insects a certain nuclear substance makes its appearance and forms a very 

 small nucleus, which, as recently shown by Blochman, gives off the ])olar 

 globules, as occurs with other animals, and forms the female pronucleus. 

 About the time of fertilization this sinks into the yolk ; a small amount of 

 protoplasm gathers around it, partly the original protoplasm and probably 

 partly that which has been produced from the degeneration of the volk 

 spherules by the ordinary process of cell growth. This nucleus and the pro- 

 toplasm around it constitute a distinct and complete cell. Division sets in 

 and a number of cells are produced. Each of these is a complete cell, 

 with plasma and nucleus, and the only relation that the yolk surrounding 

 it has to it is that of food. The subsequent history is only the increase 

 and development of these cells, and the consequent degeneration and ab- 

 sorption of the yolk. In the freshly laid egg there is inside the yolk mem- 

 bi-ane a layer of stainable protoplasm, in which are in bedded considerable 

 numbers of small, spheroidal bodies, quite highly refractile, partly fattv 

 and partly albuminous, but the main mass of the egg is made up of 

 another structure, known as yolk spherules. 



These are about .001 mm. in diameter, though varying between .0008 

 mm. and .0012 mm ; their index of refraction is not very far from that of 

 balsam : in color they are somewhat yellowish, and they do not take stains 

 readily. By mutual pressure something of their spherical shape is lost, 

 but they do not have flat sides : for those first formed are round, and the 

 later ones conform to them and so have concave sides. As to the method 

 of formation, Ave first see a very small granule, which grows gradually 

 until the full-sized yoke spherule is formed. Whether this growth is 

 merely accretion is not certainly known, but there is no indication of 

 lamination : on the other hand there is no visible spherule membrane, as 

 one would expect if the growth were due to intusseption. The method of 

 degeneration is very interesting and reminds one of the fatty degeneration 

 of the tissues of the pupa, or hystolysis. At the beginning of cell activity 

 in the egg, certain of the spherules in the immediate neighborhood of the 

 active cells begin to appear slightly granular ; the granules are coarse but 



