217 



On either side of that portion of the canalis centralis which widens 

 out and opens into the fissura rhomboidalis there are similar cells 

 (Fig. 2, a) symmetrically placed, usually two on each side; but the 

 number varies from one to three on each side. In Fig. 1 these are 

 shown (a) projected upon the median plane. Rarely, similar giant 

 cells are found which do not lie in the dorsal fissure, but laterally 

 and deeply buried in the cord (Fig. 1, ß). This condition occurs in 

 one case out of about 300. 



Size and Form. — In the youngest individuals, 3 cm in length, 

 the cells have an average diameter of 7 (.i or 8 /<. In the various 

 stages from the half-grown individual, 10 cm long, to the full-grown 

 fish of 20 cm there is a difference in the size of the cells, which keeps 

 pace with the growth of the body. In the adult there is considerable 

 variation in the size of the cells, the smaller having a minimum dia- 

 meter of 40 <u, the larger of 70 f.i, with an extreme length, to the 

 beginning of the axis cylinder, of 150 /n. The number of cells ranges 

 from 35 to 40, and seems to be fairly constant, regardless of the age 

 or size of the fish. 



The form of these giant cells, though always characteristic, is 

 quite variable. The cells show much greater regularity of form and 

 distribution in young specimens of Ctenolabrus, 3 cm in length, than 

 in the adult. In the former they lie close together in the anterior 

 part of the cord, the intervals increasing regularly posteriorly. They 

 are usually rounded, but anteriorly mutual pressure may give them 

 a somewhat angular outline. Occasionally in the smallest specimens 

 examined the cells were uniformly flattened dorso-ventrally, approaching 

 a discoid or lenticular form. 



In the adult the simplest form is approximately spherical (Fig. 6, &), 

 but this grades into the piriform, which is the most typical (Figs. I, 

 3, 10). The tapering end is ventral, and from it passes off the axis 

 cylinder. This may arise from the cell abruptly, as the stem from a 

 pear (Figs. 1, c, and 5, &), or the cell may gradually taper out into 

 the axis cylinder. In their variations of form the cells may approach 

 the ovoid (Fig. 9), the conical (Fig. 10), the discoid, or club-shaped, 

 or they may be very irregular. An interesting variation in form is 

 shown in Fig. 4, c, where the cell is apparently drawn out into two 

 parts. Every gradation, however, may be observed from the evenly 

 tapering cell (Fig. 9) through forms like those of Figs. 10, 6, a, and 4, a, 

 to the apparently double cell (Fig. 4, c). 



There arise from the cells numerous dendrites, which vary in 

 size from the finest filaments to processes of considerable diameter 



