RESEARCH PROBLEMS IN THE OPALINID^ 237 



more extensive studies of these features in the Hving opahnid, 

 though one must remember that the abnormal conditions under 

 which the animal is living while under microscopic observation will 

 soon cause distortion of at least the chromatin structures. The 

 length of time the chromatin remains "alive" under these conditions 

 can be tested by certain intravitam stains which do not color the 

 chromatin until its death (Cf. Metcalf, 1909). 



II. LIFE-HISTORY 



This, while known in outline, needs restudy as to numerous 

 important features, especially before, during and after fertilization. 

 The behavior of the metabolic chromatin at these periods needs 

 review, also especially the behavior of the genetic chromosomes, 

 for Metcalf did not properly distinguish the two in his 1909 paper. 

 This study should, by all means, be made upon binucleated rather 

 than multinucleated forms, because of their larger nuclei, their 

 smaller number of chromosomes and their greater emphasis, dur- 

 ing the vegetative phases of the life-cycle, upon the macrochromo- 

 somes and their equal division and distribution to the daughter 

 nuclei. Of especial interest are the following questions : 



i) A\Tiat is the origin of the chromatin spheres, one to four in 

 number, which appear in the nucleus and are extruded into the 

 cytoplasm during the sexual phases of the life-cycle, there to be 

 absorbed? Are they composed of metabolic chromatin only? Is 

 there left any residuum from the macrochromosomes after the 

 formation and elimination of the spheres? 



2) Is there a period of several generations when, as Metcalf 

 (1909) described, there is a haploid number of macrochromo- 

 somes, or were the macrochromosomes (metabolic) and the micro- 

 chromosomes (genetic) confused? What is the condition of the 

 genetic chromosomes during this period? This needs careful 

 scrutiny before the real nature of these important phenomena can 

 be determined. 



3) How and from what sources are the macrochromosomes re- 

 formed in the growing zygote? There are no observations upon 

 this important point. 



4) What is the exact behavior in detail of the genetic chromo- 

 somes during the whole sexual phase of the life history? Do they 

 split longitudinally at this time or at any other time? Are the 

 observable phenomena consistent with Alendelian inheritance 



