MUSEUM OF COMPARATIVE ZOOLOGY. 185 



satisfactory solution, — and for this reason : the changes accompanying 

 the metamorphosis are certainly initiated, and probably almost always 

 wellnigh concluded before the egg is laid. 



At any rate, I am sure that certain of the eggs (Fig. 39) I have 

 treated were taken immediately after deposition. They were immersed 

 in a weak preparation of acetic acid ; and yet, as before remarked, they 

 were so far advanced as to aflford little or no evidence toward the solu- 

 tion of this question. The yolk thus early subjected for several hours 

 to the action of weak acetic acid within the normal egg envelopes, and 

 then carefully freed from all enveloping substances and treated with 

 Beale's carmine, shows already two well-marked stars, whose peripheries 

 are in contact, the whole forming the figure recently named by Whit- 

 man " archiamphiaster," to distinguish it from similar figures, known 

 as " amphiasters," which arise later in the history of the egg. 



This archiamphiaster occupies the middle of the vitelline sphere. 

 The two stellate figures composing it are of equal size. Each is formed 

 by straight radiating filaments of protoplasm, which converge from 

 all directions toward an imaginary centre, which they never appear to 

 reach. 



These filaments are differentiated portions of an otherwise nearly ho- 

 mogeneous protoplasmic mass, which has a spherical form, and tolerably 

 definite, though by no means sharply marked outline. The extent of 

 these two spheres is marked by the encroachment of the coarse deuto- 

 plasmic granulations held in suspension by* the remaining protoplasm 

 of the yolk, and their outlines are consequently more or less definite, as 

 this encroachment is more or less abrupt. In no case is this so sudden 

 as totally to obscure the continuation of a few of the radiating lines, 

 for a short distance, into the more granular portion of the protoplasm. 



As at their peripheral ends, so, too, at their central extremities, these 

 filaments do not all terminate at a uniform distance from the mathemat- 

 ical centre of their respective spheres. Consequently there is a small 

 space immediately surrounding this imaginary point of convergence, 

 which, although in general of a spheroidal form, may be much less regu- 

 lar in outline than a circle, and is not very definitely circumscribed. In 

 optical section it appears as a more or less circular homogeneous " area." 

 It is only a little more deeply stained in carmine than is the surrounding 

 protoplasm. 



While most of the filaments composing the stars, or suns, are of the 

 same thickness, there seem to be a few that are rather more prominent. 

 These latter occur at intervals of 30° to 60° throughout the suns. It is 



