1888.] Gr. M. Giles — Notes on the Ampliipoda of Indian Waters. 227 



not absolute is evidenced by the existence of a distinct line free from gra- 

 nules at their point of junction, and by the circumstance that rough 

 handling has a tendency to separate the layers at this point. The rods, 

 like the cylinders, are nucleated, the nuclei lying not all in the same plane, 

 but exhibiting a tendency to alternation. These rods contain but few- 

 granules and, as already mentioned, divide below into a number of fibres, 

 each of which is continuous with a cell of the third and last layer. This 

 last layer consists of spindle-shaped cells strongly granular and dis- 

 tinctly nucleated. They are prolonged at their superficial extremities 

 into fibres, which are continuous with the branches of the rods of the 

 second layer, and their deep extremities split up into a number of fine 

 fibres, which can, in favourable cases, be made out to inosculate with 

 fibres issuing from the ganglionic mass supplying the eye. 



With such refractile arrangements, the outer surface being but 

 little curved, the entire work of refraction must be performed by the 

 lenticular bag of highly refringent fluid, and the rays, passing through 

 the transparent epidermic layer, must be brought to a focus on the 

 deeply pigmented anterior extremities of the front layer of rods of the 

 retina. The lens is probably a modified cuticular structure. It must 

 be acknowledged that so specialized a structure as this is of a higher 

 type than the very ill-developed compound eyes which are commonly 

 met with amongst the Gainmaridce. 



Nervous System. — The ventral nerve cord is large and well deve- 

 loped. In the thoracic region, the paired ganglia are placed so close to 

 each other as to nearly blend, the transverse commissures presentino* 

 scarce any constriction. In the abdominal region these commissures 

 are somewhat longer. The longitudinal commissures between the second 

 thoracic and the maxillipedal ganglia are longer than usual and diverge 

 outwards, the latter pair being placed fully the width of the oesophagus 

 apart. From these spring the long commissures of the oesophageal collar, 

 which in front join with two long, cord-like chains of cells which lie on 

 each side below the anterior prolongation of the peculiar gizzard to be 

 described below. This ganglionic cord, curving upwards, blends with 

 the main mass of the supra- oesophageal ganglion, which fills up nearly 

 the entire space of the head between the gizzard and its anterior 

 wall. From the periphery of this mass project eight rounded processes, 

 the centres of the two pairs of eyes and of the two pairs ef antennas res- 

 pectively. Those of the eyes lie almost in contact with the bases of the 

 retinal spindle cells and distinct fibrous connections can be made out 

 between them and the retina. From the long cord-like horns that run 

 back from the main brain mass to the oesophageal commissure, branches 

 may be traced to the gnathites and to the green-gland. Each of the great 

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