422 Tumors. 



cause of irregular nutrition succeed in their later growth in 

 forming only an amorphous body of all sorts of organic struc- 

 tures mixed together. This, it is likely, enclosed within the indi- 

 vidual formed from the other segmentation cells, remains without 

 further development, as a tumor. []\Iany of the so-called ovarian 

 dermoid cysts met in human beings are properly of this last 

 type, complex teratomata, frequently containing tissues evidently 

 from two or all three of the embryoblastic layers. It has been 

 suggested in addition to the above explanations for such terato- 

 mata in the sexual organs that they may be the result of seg- 

 mentation and development of an unfertilized ovum directly 

 within the ovary, a parthenogenetic development. This idea has 

 no wide acceptance, but it should be recalled that partheno- 

 genetic development is well known in many lower forms of life, 

 and that Jacques Loeb has succeeded in causing the development 

 of unfertilized ova of sea-urchins by chemical stimulation. It 

 should be added moreover that L. Loeb (Archir. f. uiikrosk. 

 Anat. It. Eutzi'icklungsgeschicht. Bd. 65, 1905) has demonstrated 

 kar3'okinetic changes and segmentation of the ovum in the ovary 

 of the unfertilized guinea-pig. The theoretical possibility of this 

 mode of origin of ovarian teratomata should therefore be accepted ; 

 although evidence of its actual prevalence is not clear.] 



