EXPLANATION OF PLATES. 391 



PLATE XLVII. 

 CYCLOSALPA PINNATA, Chain Form; Development. 



In Figure 2 of this plate the blue color of the ganglion should not extend over 

 the peri-ganglionic space outside the dotted outline of the ganglion, as it is by 

 mistake made to do on the dorsal surface between the two halves of the optic ridge. 

 Cf. Plate LI, Fig. 5, a similar section of the developing ganglion and eye of the soli- 

 tary Cyclosalpa pinnata. 



Figures 1-3, serial transverse sections of the ganglion and the first rudiment of 

 the optic ridge. Fig. 1 is the more anterior ; Fig. 3 the more posterior. The central 

 cells of the ganglion are beginning to degenerate to form the non-cellular core, gc, 

 seen in the adult and in all except the earlier stages of development. The rudiment 

 of the eye, e, has the form of a horseshoe with the open end of the horseshoe anterior. 

 The central cavity of the nervous system, /, is reduced to a mere split between the 

 dorsal two-thirds and the ventral third of the ganglion. Dorsal to this cavity are 

 seen ramifying lacunar canals, I. In places these are seen to connect with the neural 

 canal. X 300 diameters. 



Figure 4, a more anterior section from the same series, at the level of the anterior 

 face of the ganglion. It shows also a section of the duct between the ganglion and 

 the ciliated funnel, /I. X 300 diameters. (For f at the right of the figure read f. 1.) 



Figure 5, a longitudinal, vertical section of the ganglion, unpaired eye, e, and 

 ciliated funnel, cf, of an older individual. The section lies in the mid-line of the 

 body. The duct between the ganglion and the ciliated funnel is evident. X 300 

 diameters. 



Figure 6, a transverse section through the anterior part of the ganglion at a stage 

 corresponding to that represented in Fig. 5. The antero-ventral projection from the 

 ganglion is shown, v. X 300 diameters. 



Figure 7 (older stage), a vertical, longitudinal section of the ganglion and eye, on 

 one side of the mid-line. The eye, e, has assumed an almost vertical position : along 

 its posterior face the fibers of the optic nerve, on, are seen. The dorsal edge of .the 

 optic disk is curling over backward to form the second, smaller portion of the unpaired 

 eye, e'". A portion of the antero-ventral process from the ganglion, v, is shown, and 

 near it stellate cells, the remnant of the duct between the ganglion and the ciliated 

 funnel, x 300 diameters. 



PLATE XLVIII. 



Figure 1 (older stage), a longitudinal section of the ganglion and unpaired eye. 

 The rod cells have acquired definite cell walls and are commencing to elongate. X 300 

 diameters. 



Figures 2-4, horizontal sections of three regions of the unpaired eye at a stage 

 corresponding to that represented in Fig. 1. X 300 diameters. 



Figure 5 (older stage), a longitudinal, vertical section of the ganglion and unpaired 

 eye, on one side of the mid-line. X 200 diameters. 



Figure 0, a transverse section of the ganglion and unpaired eye at the same stage 

 of development as that represented in Fig. 5. X 200 diameters. 



Figures 7-9, vertical, longitudinal sections of an older eye. The eye is now nearly 

 horizontal : its three regions are clearly defined. The manner of innervation of these 

 three regions is well shown. The individual from which these sections were taken 

 was one member of a small wheel-shaped colony that had just formed on the end of 

 the stolon but was not ready to be loosed. 



Figure 10, a transverse section through the two posterior limbs of the unpaired 

 eye at a stage of development corresponding to that shown in Figs. 7-!). The posterior 

 part of the ganglion is also cut. X 300 diameters. 



