22 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



plasts (Lewitsky), Lipoid in nerve cells (Cowdry), Liposomes 

 (Faure-Fremiet) , Mammary gland secretion (Hoven), Mel- 

 anin (Asavadourova), Mucorine (Moreau), Pancreatic 

 zymogen (Hoven), Parathyroid secretion (Bobeau), Parotid 

 secretion (Regaud and Mawas), Pigment, (Prenant), 

 Poison-gland secretion (Torraca), Prepucial-gland secretion 

 (Altmann), Prostate secretion (Akatsu), Retineal pigment 

 (Luna), Sebaceous-gland secretion (Nicholas, Regaud and 

 Favre), Starch (GuilUermond), Submaxillary gland secretion 

 (Regaud and Mawas) , Suprarenal pigment (Mulon) , Supra- 

 renal secretion (Mulon), Thyroid-gland secretion (Gryn- 

 felt), Tyrosin (Asavadourova), Urea in the kidney (Oliver), 

 Venom (Grynfelt), Vitellus (Loyez), Yolk (Coghill). In 

 many instances of the above named activities, the researches 

 on which they have been based have been confirmed by other 

 investigators, and in some instances the reverse has occurred. 

 It would be quite beyond the scope of this treatise to re- 

 view and analyse all these investigations. However, the 

 researches of Levitsky ('10), Pens a ('12), GuilUermond 

 ('12a; '12b), and a host of other investigators on plast 

 formation deserve more than passing notice. A number of 

 varieties of plastids are found within the cells of plants. 

 These plastids are concerned with the production of specific 

 products in the plant. Guilliermond, in particular, has 

 conducted extensive investigations on the origin of these 

 plasts. He has apparently demonstrated the transformation 

 of mitochondria into the various kinds of plastids. His 

 work has been accepted in standard text books. Ap- 

 parently, no serious refutation of Guilliermond's work has 

 appeared. Cowdry is not inclined to accept these inter- 

 pretations on plast formation, and states that "the work 

 which has been done so far is extremely suggestive, but it is 

 not conclusive." It appears that the assumed fixed phos- 

 phohpin-albumin constitution of mitochondria has in- 

 fluenced Cowdry 's criticisms. The living properties of 



