56 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



asexual — and possibly sexual — generations behind them, that the beginning of 

 many of the nietazoan organs must be looked for and not in subsequent aggre- 

 gates of differentiated cells. 



In no place is this obvious relation of the Protozoa and Metazoa more 

 strikingly illustrated than in nuclear conditions which obtain throvighout the 

 two groups. The older method of beginning all cytological study of nuclear 

 phenomena with Ascaris, or other metazoan types of a relatively late period 

 of evolution, is an inversion of the natural order. Recent investigations are 

 continually bringing to light knowledge of nviclear and mitotic phenomena in 

 the Protozoa, which may ultimately result in a considerable reorganization of 

 many of our present day concepts of these conditions in the Metazoa. 



Ocelli. — In the possession of a well developed eyespot or ocellus the 

 Pouchetiidae stand imique among the Protozoa. In its type of structure this 

 organ is distinctly metazoan in character, apart from the fact that it forms 

 only part of a single cell instead of being made up of a number of cells united 

 in specialized tissues. From the larger viewj^oint of the body as an integrated 

 organism, and not as groups of cellular tissues, this aspect of its lack of cellular 

 organization is of relatively minor importance. 



Schiitt, in his monograph on Die Peridineen (1895), places the stigma, or 

 eyespot, as it is sometimes termed, of the fresh-water dinoflagellates, as in 

 GJcnodinium cinctum, in the same category as the ocellus of Pouchefia, as did 

 Biitschli (1885) in his earlier discussion of this subject. Later biologists, as 

 Lang (1901), Doflein (1911), and Liihe (1913), add to this category the stigma 

 of fresh-water flagellates, as in EugJcna and Eudorina. The basis of these later 

 comparisons seems to lie in the early investigations of France (1893), which 

 have not, however, been confirmed by later investigators working on the same 

 forms. 



France figured for EugJena, Eudorina, Pandorina, and Trachelomonas 

 stigmata of a peculiar type. In each of these flagellates this structure consisted 

 of a mass of red pigment imbedded within which were small spherical bodies. 

 These bodies varied in number from one to two or more in the different species. 

 They were spherical or ellipsoidal in shape and highly refractive. In Euglena 

 these bodies were composed of paramylum and in the Phytoflagellata of 

 amylum. 



The later work of "Wager (1899) and Hamburger (1911) on Eur/lena and 

 of Kofoid (1898, 1899) on Pleodorina and Platydorina cast considerable doubt 

 on the validity of France's work. Both Wager and Hamburger found in 

 Euglena viridis that the stigma is composed of small red granules imbedded in 

 a protoplasmic layer. The stigma lies on the border of the cytopharynx in 

 close relation -^ith a slight enlargement of the flagellum. No "crystallin" or 

 '^'lens bodies" could be found in any of the material under examination. In 

 Pleodorina and Platydorina the stigmata are sunple masses of pigment gran- 

 ules, with no differentiated structure. Other examples might be mentioned, but 



