256 Robert Wilhelm Hegner. 



Mesodermzellen der letzteren die Genitalfollikel." A strand of cells 

 was fonned on either side of the body and from each, in the female, 

 five pairs of follicles arose and were distributed in segmental order 

 from the second to the sixth abdominal segment. In the male, 

 double pairs of follicles occurred in the fourth to the sixth abdominal 

 segments. There were thus produced twelve ''Hodenfollikel" and 

 ten egg-tubes. 



Verj little attention has been directed to the early development 

 of the germ-glands in the Collembola^ but several embryologists have, 

 however, made observations on the later stages of these organs. 



Claypole (1898) described two methods of origin of the germ- 

 cells in Anurida ^naritima. In the first case a germ-cell was found 

 lying in the cavity of the mesoblastic somite of the second abdominal 

 segment ; this gave rise to a mass of cells, the germ-gland, situated 

 between the splanchnic and somatic layers of the mesoderm. Later, 

 the germ-gland appeared to break through the mesoderm and come in 

 contact with the yolk. The ovaries which developed in this way were 

 found to contain many yolk globules lying among the germ-cells. 



In the second case, Claypole states that a single germ-cell passed 

 out from the wall of the mesoblastic somite into the yolk ; it produced 

 an irregular mass of cells lying partly in the mesoderm and partly 

 in the yolk. The cells of this group migrated inward becoming 

 scattered among the yolk-globules. The next period in the history 

 of these cells was not found. The final stage found by this author 

 represented the germ-gland of the male ; it was an oblong structure 

 directly connected with a large irregular sac of yolk. 



The ovaries of ten species of Collembola were studied by Lecaillon 

 (1901). In Sira nigromaculata, just after hatching, the female sex- 

 organs were described as "deux petites masses ovoides placees dans 

 la cavite generale du corps, a pen pres a egale distance de I'extremite 

 anterieure et de I'extremite posterieure de 1' abdomen." They were 

 situated ventrally between the third and fourth abdominal seg- 

 ments. The germ-glands of Tomocerus plumheus and Templetonia 

 nitida were found to occupy a position similar to that described 

 above. In Templetonia, however, "les dimensions de la chambre 

 gonadiale surpassent notablement celles du meme organe chez les 

 deux cspcces precedentes." 



