No. I.] POLYCHOERUS CAUDATUS. i6l 



mum. With a very low power lens this stage is easily distin- 

 guishable by its red spot, which becomes later a little more 

 diffused, and then gradually fades out before the embryo is 

 formed. 



The pigment granules which characterize the adult, as de- 

 scribed by Mark (i), are of a totally different form and color, 

 and bear no resemblance whatever to those which occur in the 

 ovum. I have examined many animals by crushing them under 

 a cover slip, but have found nothing resembling these pigment 

 granules. If they occur at all in the adult, which I doubt, they 

 are very few in number and therefore difficult to find. So, also, 

 in the immature ovum these pigment granules are rare if they 

 occur at all. The young worm just hatched is marked by 

 granules similar to those formed in the adult, while none or 

 almost none of the above described granules are to be found 

 in it. 



In the ova of an undescribed species of Aphaiiostoma {)), 

 which is found in this vicinity, and to which my attention was 

 first called by Professor H. C. Bumpus, a precisely similar 

 arrangement and movement of pigment granules, if they be 

 pigment granules, occurs. They are distinctly larger and redder 

 than those found in the ova of PolycJioerus, and the dividing 

 line between the two halves (Fig. 32, a) is more distinctly 

 marked. This Aphanostoma (?) is a dark green color, and no 

 red pigment is to be found in it, and the ova when newly 

 laid, have a color very similar to that of the parent. Soon, 

 however, the red pigment appears on the upper pole, and as 

 segmentation progresses is finally collected on the opposite 

 pole, forming the red spot similar to the one just described, 

 but more brilliant in color. Experiments similar to those 

 detailed by Haberland (7) to prove whether these granules 

 might not be independent organisms, were attempted, but the 

 results were perfectly negative. The ova died very soon and 

 the pigment granules disappeared entirely. 



A very remarkable phenomenon during the segmentation of 

 the ova of Polychoenis is the manner in which the ovum changes 

 its form and becomes distorted, as if some internal forces were 

 pressing in different directions ; also the marked difference 



