630 



FERTILIZATION 



by further investigation, but it seems reasonable on the basis of the avail- 

 able facts and is in line with current theory. 



Calkins (1919) describes a peculiar situation in Uroleptus mobilis, 

 in which two types of metaphase stages are found (Fig. 149), one in 

 which about twenty-four chromosomes appear and twelve go to each pole, 

 and another in which eight chromosomes appear and eight go to each 

 pole in an obviously equational division. Although the number is not 

 strictly homologous, the first type is similar to that which occurs in 

 Euplotes patella and other species, and the second type is what would 

 be expected if all chromosomes were compact. Intermediate forms are 

 conceivable, in which some chromosomes are compact and others are 



Figure 149. First maturation spindles of Uroleptus mobilis. A and B, two types of 

 metaphase stages; C and D, two types of anaphase stages found in this form. Both 

 types are equational divisions, since the diploid eight chromosomes appear in the sub- 

 sequent division, in which they are reduced to four. (After Calkins, 1919.) 



dispersed as several loosely associated chromomeres. This would explain 

 many irregular counts, which otherwise seem chaotic. 



In Chilodonella [Chilodon) uncinatus a parachute is formed after 

 the division of an endobasal body, according to MacDougall (1925). 

 Enriques (1908) failed to see the parachute in the same species, but 

 described a peculiar rod formation. In MacDougall's material, four 

 strands of chromomeres are formed from the spireme of the late para- 

 chute stage and condense into four dumb-bell chromosomes on the 

 spindle. This author states that the exact number of granules in each 

 strand was not determined, but her Figure 23 shows four on each strand. 

 This is interesting, since four chromomeres to a chromosome has been 

 found in E. patella (see Fig. 148 E) and other ciliates. The four chromo- 

 somes then split longitudinally and four halves migrate to each pole, at 



