138 FOOT AND STROBELL. [Vol.11. 



which we have been able to see chromosomes within the spindle 

 led us at first to think that the living eggs which showed this 

 exceptional feature must be abnormal, for, as a rule, the chro- 

 mosomes are not visible until the <^^^ dies naturally, or is killed 

 by a fixative. It was not until we were able to watch an egg 

 develop normally after the chromosomes were seen, that we 

 were convinced these exceptional cases were due to other 

 causes. This does not appear to be wholly dependent upon 

 the position of the spindle, for often in cases where the spin- 

 dle is in the most favorable position, and clearly indicated, the 

 chromosomes cannot be seen, even with the highest powers. 



Text-fig. Ill represents a living oocyte, first order, taken 

 from a freshly deposited cocoon. The chromosomes at the 

 metaphase were so distinct that two of them were readily 

 traced with the camera. We watched this ^^^ until it con- 

 stricted off its first polar body, and then we killed it in chromo- 

 acetic, stained and hardened it, and in every respect it appeared 

 to be a normal oocyte, second order. We would accentuate the 

 fact that the chromosomes in the living egg showed exactly the 

 same form as those seen in sections, as this possibly indicates 

 that the chromosomes are less sensitive than the cytoplasm 

 to the action of the fixatives. The fact that these centers of 

 activity are more staple than the cytoplasm, one of us suggested 

 in a former paper (7), where it was stated that the pronuclei 

 continued to develop long after the cytoplasm was unquestion- 

 ably abnormal. 



The ^^^ represented in Text-fig. Ill was below the average in 

 size, thus transmitting relatively more light ; this fact probably 

 accounting, in part, for the relatively distinct outlines of the 

 structures within the Q.gg. The broad, clear rays, which could 

 be traced from the attraction sphere almost to the periphery, 

 do not appear to correspond to the rays so clearly outlined in 

 chromo-acetic sections (Photo. 15), but rather to those of osmic 

 acid sections (Photo. 17). This photograph is technically poor, 

 owing to the fact that it is taken from a section lo/i thick. It 

 is introduced only because it is the best example we have (in 

 sections) of a structure that can be compared to the rays of 

 an attraction sphere in the living ^%^. We are not yet pre- 



