Gorin-Cclls in Clirysoiiielid Beetles. 237 



zellen," as Weismann called them, consisted of homogeneous proto- 

 plasm containing a nucleus and one or two yolk-granules. Weismann 

 thought ^'dass der Modus ihrer Genese innerhalb des Begriffes von 

 der freicii Zcllcuhildung tallt, wie ilui die iUtcre liistologische Schule 

 aufgestellt hat." The four primitive pole-cells divided each into 

 two, sometimes even before they were entirely separated from the 

 egg; these resultant eight pole-cells became confused with the develop- 

 ing blastoderm-cells, and Weismann could not follow them further. 



Neither Robin nor Weismann realized the importance of these 

 pole-cells and it remained for Metschnikoff (1865) and Leuckart 

 (1865) to announce their true significance. Leuckart (1865) de- 

 scribed their formation in the p^edogenetic larva of Miastor and con- 

 firmed Mctschnikoff's (1865) statement that they were really the 

 primitive genn-cells and entered into the constitution of the pseudo- 

 varium. Leuckart could distinguish the single nucleus of the primi- 

 tive pole-cell when there were only eight to ten nuclei in the 

 pseudovum. 



A year later Metschnikoff (1866) gave a more detailed account 

 of the history of the pole-cells in Simula sp. and Miastor. In Simula 

 four to 'five pole-cells were present at the posterior end of the egg, 

 each containing a nucleus and very fine yolk-granules. In Miastor 

 the genesis of the pole-cells was traced more accurately than in 

 Simula. Eggs were found containing only two nuclei which were 

 supposed to result from the division of the germinal vesicle. These 

 nuclei continued to give rise to others by division until twelve to 

 fifteen were produced, one of which, lying at the pointed pole of the 

 pseudovum, became surrounded by a thick, dark yolk mass and with 

 it separated as a distinct membraneless cell, the first pole-cell. This 

 then divided into two and later into four cells. These four then 

 separated into two groups of two cells each and were recognized as 

 the primitive reproductive organs lying in their definite positions. 

 The two large pole-cells of each gTOup were already divided and 

 enclosed in an epithelial layer of embryonic cells at the time of 

 hatching. 



Grimm (18Y0) described in the parthenogenetic eggs of a species 

 of Chiro'n omits, a membraneless cell which divided into two, then 



