THE SPERMATOGENESIS OF AGALENA N/EVIA. 137 



only one of the chromosomes can be followed uninterruptedly 

 from the spermatogonium to the spermatid, that even during the 

 growth period the chromosome form is maintained, then we must 

 say that in our preparations Anasa tristis supports in a very re- 

 stricted sense, if at all, the theory of the " Individuality of the 

 Chromosomes." 



While all agree that the term individuality should not usually 

 be taken in its narrowest sense in reference to chromosomes, the 

 general fact that the same number of chromosomes issues from a 

 reticulum as passes into it and that they have been seen to re- 

 appear in the same positions within the nucleus, added to strong 

 evidence found in studies of fertilization of the egg of Ascaris and 

 other forms, seem to me to clearly indicate genetic connection 

 between the chromosomes in successive cell-generations. Even 

 if the chromosomes do resolve themselves into their component 

 granules which are distributed on a linin reticulum, it is not 

 difficult to conceive of each one thus spreading out along definite 

 lines, its ultimate branches temporarily anastomosing with those 

 of adjacent ones, as a method of interchange of material or as a 

 method of gaining nutriment for each granule which would be 

 much less easily done in the dense, compact form. The proba- 

 bility is that the so-called resting stage is a stage in which 

 physiological activity of the chromosomes is at its height. An 

 Amaba, whether it be in an encysted form or whether it be 

 spread out into a protoplasmic mass of extreme delicacy, with 

 numerous pseudopodia, is still an individual Amceba. 



In Agalena, the ordinary chromosomes offer no strong evi- 

 dence in favor of chromosomal continuity although the loops of 

 the spireme differ in length and in the prophase of the primary 

 spermatocytes some of the V-shaped chromosomes differ slightly 

 in size. One of these which opens at a much wider angle than 

 the others recurs again and again, and is probably always present 

 at this stage. When we turn to the accessory chromosomes, on 

 the other hand, we find that they stand a more severe test than 

 that outlined above and even comply with the demands of Foot 

 and Strobell when they claim that, to meet the requirements for 

 individuality, several or only one of the chromosomes should be 

 followed uninterruptedly from the spermatogonium to the sper- 



