20 QUATERCENTENARY STUDIES IN PATHOLOGY 



thonous" tcratomata, which have recognisable parts of a second foetus, 

 he admits have origin in a second embryo. 



Marchand {^'^) looks on the higher foetus like forms of epignathus as 

 asymmetrical double malformations. He draws attention to the fact 

 that epignathus is a parasite in intra-amniotic relation with the autosite. 

 Hence he says there must have been an unequal division of a single 

 embryonal anlage. 



He thinks the origin of epignathus is most likely from the fertilisation 

 and development of a polar body. 



Bonnet (7) upheld this hypothesis, but went further, suggesting the 

 possibility of the belated division of one or more blastomeres, in an early 

 stage of segmentation. 



Wilms (^^) also supported the same view with regard to teratomata 

 of the ovary and testis, and held that certain details of their structure 

 pointed to an origin from blastomeres. 



Windle, in speaking regarding the mass of germ plasm out of which 

 the major forms of epignathus are developed, suggests the theory that " it 

 is not the equivalent of a germ plasm of full embryo-producing power, 

 but that it possesses varying and more limited potentialities of develop- 

 ment." 



Beard (4) applies his doctrine of multiple germ-cells to explain the 

 origin of tumours. He considers that the early blastomeres of a 

 metazoon form "an asexual foundation or larva, the phorozoon, upon 

 which the germ-cells, and with these an embryo, take their origin." 

 Normally, one of these germ-cells undergoes development, but two or 

 more may develop. If two primary germ-cells "develop either together 

 or at different times, but with abnormalities on the part of one, there 

 may result a more or less rudimentary embryo, an embryoma of Wilms, 

 a tumour." 



E. Schwalbe accepts the view that the higher foetus forms owe 

 their origin to a blastomere, which in an early stage was disturbed from 

 the development of the autosite. He allows the possibility of an origin 

 out of germ material of a later development stage. He points out that 

 the prospective potency of blastomeres always becomes more circum- 

 scribed with progressive development. Through an unequal division of 

 the blastomere material, or through a disturbance of a blastomere at a 



(194) 



