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+ 
106 BULLETIN OF THE 
Gonodactylus (Fig. 101) the retinular cells are certainly as numerous 
as in Squilla; but seven obvious cells in the retinula, as I have already 
shown in Mysis, may suggest the presence of eight in all, one of them 
being rudimentary. This condition is in fact characteristic of Gonodac- 
tylus also, as can be seen in the series of ommatidia shown in Fig. 100. 
These six ommatidia represent consecutive individuals in one of the 
’ bands of larger ommatidia previously mentioned. The band as a whole - 
is cut obliquely, and in such a way that the ommatidia from 1 to 6 are 
cut successively in deeper or more proximal planes. In ommatidium 1 
the rhabdome is surrounded by seven retinular cells, four of which are 
upon the right side and three upon the left. In addition to these, a 
large nucleus (nl. pz.) lies close to the rhabdome. Ommatidium 2 has 
essentially the same structure as ommatidium 1. In ommatidium 3 the 
nucleus corresponding to the one seen in ommatidium 1 and 2 is no longer 
visible, but in its stead there is a small mass of granular protoplasm. 
A similar mass is also seen in ommatidia 5 and 6. It is usually pres- 
ent directly proximal to the nucleus figured in ommatidia 1 and 2, and 
is, I believe, the protoplasmic body of the cell to which this nucleus 
belongs. In ommatidium 4, the seven nuclei of the seven large (func- 
tional) retinular cells can be seen. These nuclei appear very large in 
transverse section compared with the cells in which they occur. It is 
probable that the cell wall is distended by them, although, owing to the 
indistinctness of the cell boundaries, I have not obtained positive evi- 
dence of this. In ommatidium 6 the seven retinular cells are seen in 
section at a plane proximal to that in which their nuclei lie. As in 
ommatidium 1, three of them are upon one side of the rhabdome 
and four upon the other. In a part of the ommatidium more proxi- 
mal than that shown in number 6 (Fig. 100), the transverse section 
of the retinula has the appearance seen in Figure 101. Here the 
retinular cells have the same relation to the rhabdome that they do in 
ommatidium 6 (Fig. 100), except in the case of the upper right-hand 
cell of that figure. This cell enlarges in its more proximal portion, and 
comes to occupy a position directly below the cell whose nucleus is shown 
in ommatidium 1 (Fig. 100). The gradual disappearance of this distal 
cell as one proceeds in a proximal direction from the plane of number 
6, Figure 100, to that of Figure 101, and the gradual shifting in the 
position of the cell which replaces it proximally, can be followed so 
easily that there is not the least question as to the accuracy of the 
relations described. It is evident, then, that in Gonodactylus, as in Mysis, 
the retinula consists of eight cells, one of which is rudimentary. 
