6 THOS. H. MONTGOMERY jr., 



Ascaris ovum as defined by Van Beneden ('83), the term "Centro- 

 deutoplasma". 



V. Erlanger ('97 c) gives a general review of the phenomena of 

 chromatin reduction in male sexual cells, including the papers of 

 Wilcox, Toyama and Vom Rath. 



GiARDiNA ('97) gives a preliminary note on the chromatin reduc- 

 tion of Mantis, without any figures. "In the equatorial plate of the 

 2nd pole spindle are 14 chromosomes . . . that is, there are observed 

 in the nucleus of the 2nd pole body and in the female pronucleus 7 ; 

 at the first division of the spermatogonia there are 14 chromosomes 

 at each pole plate. In the 1st maturation spindle of the male elements 

 are 28 chromosomes regularly arranged 2 to 2, i. e. 14 double chromo- 

 somes; then the chromosomes of each group separate, one goes to 

 one pole and one to the other, remaining for some time united by 

 an achromatic filament. The pole plate of the 1st spindle becomes 

 immediately the equatorial of the 2nd, where the 14 chromosomes are 

 arranged in pairs, of each of which one goes to one pole and one to 

 the other. There are therefore 7 chromosomes in each polar platei 

 which becomes the resting nucleus of the spermatid. The disposition 

 of the chromosomes in pairs, observed in the equatorial plate of the 

 2nd direction spindle, has relation perhaps with the tetrad . . . .; in 

 which case the 1st division has the value of equation and the 2nd of 

 reduction." 



Henking ('90 b) gives an excellent account of the spermatogenesis 

 of Pyrrhocoris^ to many details of which more special reference will 

 be made in the descriptive part of the present paper. In the sper- 

 matogonia and tissue cells are 24 chromosomes. In the prophases 

 of the 1st spermatocytes occur typically 12 rings, each of which has 

 the value of 2 chromosomes; but frequently a greater number than 

 12 separate chromatin elements is observed, in which cases a number 

 of the elements have the value of only one chromosome each. "Wir 

 müssen uns hier demnach mit dem sichern Nachweis begnügen, dass 

 vielfach in den zur Theilung sich anschickenden Spermatocyten eine 

 grössere Zahl als 12 getrennte Elemente angelegt wird, wobei von dem 

 Unterschiede zwischen ein- und zweiwerthigen Elementen abzusehen 

 ist." In the equatorial plate the 42 spherical elements become arranged 

 in two rows, one above the other, so that "überall die Kugeln zwei- 

 werthige Elemente bilden, welche paarweise in der Richtung einer die 

 Kerntheilungsfigur verbindeueu Achse neben einander liegen. Man 

 bekommt demnach vom Pol aus stets 12 Kugeln zu Gesicht. . . . Ich 



