REFERENCE LETTERS.
| a | = | flagellum in [Fig. 27], that is supposed to extend centrad beyond the nucleus. |
| b | = | twin flagella in [Fig. 27], of which the centrad continuation is seen applied against the distal surface of the cells and to be continued centrad. |
| c | = | capsule of lens. |
| cf | = | axial fibers of cells extending centrad. |
| co | = | cornea. |
| concr | = | concretion cavity. |
| ec | = | ectoderm. |
| en | = | endoderm. |
| f | = | flagella. |
| flp | = | distal fiber of a long pigment cell. |
| fpr | = | axial nerve fiber of a prism cell. |
| fpyr | = | axial nerve fiber of a pyramid cell. |
| frc | = | axial nerve fiber of the retinal cells of the simple eyes. |
| gc | = | ganglion cells. |
| ind | = | impression of the lens probably due to the pressure of weight against the surrounding tissue. |
| l | = | lens. |
| lp | = | long pigment cells. |
| m | = | muscle fibers. |
| namp | = | nuclei of ampulla cells. |
| nc | = | network cells ([Figs. 13 and 16]), and nettle cells ([Figs. 28, 29]). |
| nf | = | nerve fibers and tissue. |
| nlp | = | nucleus of long pigment cell. |
| nm | = | nucleus of muscle cells. |
| nprc | = | nucleus of prism cell. |
| npyrc | = | nucleus of pyramid cell. |
| nz | = | nuclear zone. |
| pr | = | prism of prism cell. |
| prc | = | prism cell. |
| pyr | = | pyramid of pyramid cell. |
| pyrc | = | pyramid cell. |
| pz | = | pigmented zone. |
| r | = | retina. |
| s | = | secretion in endo. of tent. and ampulla. |
| sh | = | shrinkage space. |
| sec | = | vitreous secretion in the lumen of the simple eyes. |
| sla | = | supporting lamella. |
| vb | = | vitreous body or zone. |
| x | = | (1) the approximate level at which [Fig. 4] should be cut transversely to give [Figs. 1 and 3]. (2) the thickening of the supporting lamella in [Fig. 13] to support the lens. |
| * | = | Point of approximation of cells of lenses in Figs. [7] and [13]. |