116 BULLETIN OF THE 
under the head of Cone Cells indicates the occasional occurrence of cones 
containing only four cells, although the usual number is five. In the 
line for Serolis, under the head of Corneal Hypodermis, the parenthesis 
and included signs are intended to indicate the possibility of there being 
more than two cells in the corneal hypodermis for each ommatidium. 
In the Schizopods, Stomatopods, and Decapods, the number of prox- 
imal retinular cells is expressed in the form of 7 +1 instead of 8, be- 
cause one of the cells is rudimentary. 
THE INNERVATION OF THE RETINA. 
The innervation of the retina in the compound eyes of Crustaceans is 
chiefly interesting, because of its importance in relation to physiological 
questions. As this paper deals with a morphological topic, it would be 
obviously irrelevant to enter upon any extended discussion of this sub- 
ject. Nevertheless, the innervation of the retina is not without some 
bearing on the general question which I have set for myself, and I shall 
therefore not pass it by, but put in as brief a form as possible what I have 
observed concerning it. 
In my account of the retina in the lobster, I described the optic- 
nerve fibres as terminating in the proximal retinular cells. Near the 
ganglion each fibre consists of a bundle of fibrils, simply enclosed 
within a sheath, but as it approaches the retina it becomes coated with 
pigment. The pigment increases in quantity and the fibre correspond- 
ingly enlarges till it finally becomes continuous with the deeply pig- 
mented retinular cell. The fibrillar axis can be distinguished in the 
pigmented portion of the fibre as a transparent axial structure, and it 
can also be traced distally through the pigment of each retinular cell 
till it breaks up into its ultimate fibrille, which are spread over the dis- 
‘tal half of the rhabdome. This is the method of nerve termination in 
the lobster, and points very conclusively to the rhabdome as the termi- 
nal organ. : 
What I have seen of the termination of the nerve fibres in other 
Crustaceans confirms the account which I have already given for the 
lobster. In some species which I have studied, owing to the small size 
of the retinal elements, I was unable to determine the cells with which 
the nerve fibres connected. The termination of the fibres in the cells 
of the retinula was observed, however, in the following genera: Bran- 
‘chipus, Limnadia, Pontella, Gammarus, Talorchestia, Idotea, Porcellio, 
Spheroma, Serolis, Gonodactylus, Mysis, Palemonetes, Crangon, Cam- 
