CYTOPLASMIC INCLUSIONS 147 



divides the tube in two parts, each of which continues to function in the 

 daughter cells (Bush, 1934). The only possible exception would be the 

 stages in which the parasite is transferred from one host to another. The 

 new vacuolar apparatus of Paramecium is said to arise by the multipli- 

 cation of canals and by the division of the whole vacuolar apparatus just 

 prior to fission (Nassonov, 1924). The formation of extra vacuoles has 

 been noted many times in living ciliates, but there is no recorded observa- 

 tion of the actual division in a living Paramecium, and the interpretation 

 of Nassanov's figures of fixed material is susceptible to the difficulties 

 inherent in building any cycle from fixed material alone. 



The majority of vacuolar systems, however, do not possess the thick, 

 permanent wall similar to that in Haptophrya, but a temporary aqueous 

 vacuole which certainly arises de novo (Taylor, 1923; Day, 1927; Mac- 

 Lennan, 1933, 1936). These vacuoles and their membranes are not 

 osmiophilic, the impregnation of the vacuolar system being due to the 

 aggregation of the osmiophilic excretory granules. The fundamental 

 question with respect to the origin of Golgi bodies is in these cases not 

 the origin of the vacuoles, but the origin of the individual excretory 

 granules. These granular aggregations in the Ophryoscolescidae have 

 been observed in living specimens (Figs. 53-55) to be ectoplasmic Golgi 

 bodies which migrate into the region of the vacuole during systole and 

 the earliest stages of diastole (MacLennan, 1933). In specimens fixed 

 during division of the ciliate, the newly arising vacuolar regions some- 

 times overlap the old ones and give the appearance of a division of the 

 old one as described in Didinium (von Gelei, 1938), but a study of 

 similar stages in living ciliates shows that they originate independently. 

 These granules are continually migrating toward the vacuoles and dis- 

 solving there, and no granules migrate outward, so the question of origin 

 is shifted to the granules at the time they are scattered in the ectoplasm. 

 No cases of division were observed, either in fixed or in living material, 

 at any place nor at any stage of the life cycle. This negative proof is not 

 entirely satisfactory, since these granules are small (0.25 — 0.50 [/.) and 

 a very rapid division might escape notice. This problem does not occur 

 in Ichthyophthirius, since all ectoplasmic granules (whether scattered or 

 around the vacuoles) are absent in the encysted stage (MacLennan, 

 1936), so that in this ciliate they must originate de novo in the young 

 parasites, whether or not they continue from them by division as the 



