No. 6.] AMERICAN MORPHOLOGICAL SOCIETY. 357 



directly from the front end of the acusticum. Evidence for 

 this from Acipcnscr : 



a. Gross continuity of cerebellum and acusticum. 



b. The root fibres of the fifth, eighth, and lateral line nerves 

 enter and end in both. 



c. The several categories of types of cells in the cerebellum 

 -Purkinje cells, granules, and cells of the second type --are 



strictly homologous with similar cells found in the acusticum. 



d. The development of the Purkinje cells in the acusti- 

 cum from the typical large cells of that nucleus is in actual 

 progress and may be studied in all its stages. 



Additional evidence in Petromyzon : 



a. The Purkinje cells in the cerebellum are not well devel- 

 oped, and their neurites run to the base of the mid-brain, 

 possibly having the same destination as the internal arcuate 

 fibres from the acusticum. 



b. The tracttis tecto-cerebellaris seems to be absent and the 

 tractus lobo-ccrebellaris is small. 



c. The cerebellum is little more than a dorsal arch and 

 commissure from the front end of the acusticum. 



XXII. ASEXUAL REPRODUCTION OF PLANARIA 



MAGULATA. 



WINTERTON C. CURTIS. 



THE fission of Planaria maculata, while it does not differ 

 essentially from the type found in other planarians where fis- 

 sion occurs, is of just the right sort to complete a very interest- 

 ing series and connect the fission of land planarians, which 

 is hardly more than a fragmentation, with the fission of 

 Planaria fissipara, in which the organs are completely formed 

 before the new individuals separate. This series is as follows : 

 (i) Land planarians, in which pieces of varying lengths are 

 pinched off from the posterior end; (2) Planaria maculata, 

 which divides always at the same place behind the pharynx, 

 with no preformation of organs; (3) Planaria subtentacula 



