216 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



the metencephalon and niyelencephalon only were available for study. 

 Eeissner's fibre is of large size, measuring from 5 to 8 micra in 

 diameter. 



Batrachoididae (198). In the toadfish, Opsauus tau, Eeissner's fibre 

 has a diameter in the canal of 1.5 micra, the lumen of the canal being 

 45 to 50 micra in diameter. 



Gadidae (214). Four species of this family have been studied, both 

 in larval and adult stages. In the larvae of the common cod, Gadus 

 callarias and Gaidropsarus argentatus, from 1 to 3 cm. long, Eeissner's 

 fibre has a diameter of 0.5 to 1.0 micron. It is formed from numerous 

 fine fibre-like bundles of axons of the torus-cells, most of which enter 

 the ventricle through the ' Schaltstiick ' (Plate 7, Fig. 52), a lesser 

 number emerging from the anterior end of the ventral fissure of the 

 torus. 



In Microgadus tomcod, at the anterior end of the mesocoele (Plate 10, 

 Fig. 70), Eeissner's fibre breaks into divisions which enter the brain 

 tissue separately. The main division enters immediately cephalad of 

 the posterior commissure, breaking up into many fibrils as soon as it 

 is within the tissue. These fibrils are made up largely of the axons 

 of the torus-cells, which lie immediately anterior and dorsal to the 

 posterior commissure. Another branch enters the brain tissue anterior 

 and dorsal to the commissure, and breaks up into numerous sharply 

 defined trunks, which, being intermingled with coarse neuroglia fibres 

 (/5r. e'end.), are difficult to follow. One branch of the fibre was observed 

 to pass directly through the commissure. This condition has been seen 

 in other species, and at first seemed most anomalous. But as the cells 

 of this apparatus have already sent their axons into the ventricle before 

 the posterior commissure is fully developed, it is easy to see how, through 

 the subsequent growth of the commissure, this condition may be brought 

 about. 



Pleuronectidab (219). The apparatus has been studied in sagittal 

 and transverse sections of Paralichthys dentatus and Pseudopleuronectes 

 americanus, in which there are no essential differences. The torus-lobes 

 (Plate 9, Fig. 62, fo7'. Ig.) are distinct, flattened, and pad-like, having a 

 somewhat rounded rectangular outline in cross-section. Posteriorly 

 they are in close contact with the large valvula, and taper away at 

 about the middle of the mesencephalon. (For the morphology of the 

 torus see also Sargent, :03'', Figs. 11-14.) The axons of the torus- 

 cells run toward the dorsal and median line, fusing into close bundles, 

 and some fine trunks pass into the median fissure above the posterior com- 



