No. 636] POLYEMBRYONY IX TJIK Ah'MAnH.I.O (57 



importance that the produetion of (ni;i(ifiii>l<'t^ from the sinfrle 



while the experimental attempts to produce t\\iiis ;nid double 

 individuals in fish eorgs and other forms have <rivon at l)est only- 

 small percentages of snch individuals amonfT tlie larjre jrroups 

 of egj?s treated. It is also a fact that all c^'-frs do not furnish 

 equally favorable material for artificial twin pwduction. The 

 ejrgs of the trout seem unquestionably more disposed to grive rise 

 to twin formations than do the eprfrs of Fundulus. Thus some 

 efr«:s would seem to have a hereditary or truly innate pre- 

 disposition towards polyenil)ryonie formations. TImm-o is much 

 reason to believe that asid(> from tlie cxt.M-i);il f.-irtors di^mssi'd. 

 the armadillo ec^g it.self i^ liio^lily divp s,.,l tow aid tli. foi'in,/ 'on 

 of accessory embryonic buds. 



There is the possibility, of course, tliat llii.s natural experiment 

 with the armadillo efr? has become so exactly rennlated as to 

 influence the developmental pntcesses ])r<>iMsely the same way 



not a ca.se of simple twin pwths from the blastoderm, but as 

 Patterson finds, there are primarily two buds, and then very 

 promptly two secondary ones arise makinor four and after 

 this the bnddin- ])roees> .-ease.s. Tn lie- S.nitli Amerirau vpeeie^, 



hio-lHu- vertebrates. T^ut llie posMbility for surli expr.-ssi.ai mijrht 

 only exist on account of the delay in implanlation of the bla^^to- 

 cyst and consequent shor'tafre of the oxyrren .supply necessary for 

 the rapid formation and frrowth of the sincrle eitd)ryo. 



