256 RECORD OF CURRENT RESEARCHES RELATING TO 



ganglion. With the superior mass a trifid eye is connected, which 

 is placed in a depression of the body and is unpaired ; the three 

 constituent parts (simple eyes) are placed one on either side of a 

 median one ; in each of these it is possible to distinguish a crystalline 

 lens and an internal portion filled with a very dark colouring 

 matter ; each " optic cell " is surrounded by a pretty firm integu- 

 ment ; but it is still impossible to say how it is innervated, for as it 

 lies directly on the tip of the most anterior portion of the supra- 

 oesophageal ganglion, it seems impossible to speak of any proper 

 optic nerve. The nerve-relations of the first pair of antennae are, 

 however, sufficient to demonstrate their sensory fimction ; nerve- 

 fibres pass into the tactile processes with which these structures are 

 supplied, and just before they so enter, the fibre is connected with an 

 ovate or spindle-shaped cell. The caudal furca has a very similar 

 nerve supply. Another set of sensory organs are to be found in 

 the tactile setae which are scattered over the whole of the body ; these 

 are solid hairs, generally provided with a number of processes, and 

 connected by a duct running through the carapace into the subjacent 

 tissues ; this duct is filled with a granular protoplasm, in which a 

 rounded or somewhat oval nucleus may be distinguished, and there is 

 supplied to it a delicate filament which is apparently a nerve-fibre. 



Other organs of less evident function remain to be considered. On 

 the inner side of the basal joint of the second pair of maxillipedes 

 there is a small elevation, which is covered with small, closely-set 

 hooks. Careful observation is necessary before one can detect in 

 the midst of these a delicate, sharply-ending process. The author 

 compares their arrangement with what was seen by Vejdovsky in 

 Tracheliasies, and taken by that observer for a sensory organ ; but in 

 neither case was it possible to detect the entrance of any nerve-fibre. 

 On the ventral surface of the cephalothoracic region there are two 

 pairs of processes ; one set are elongated and are covered by a fine 

 and delicate integument, while they contain the same granular ground- 

 substance as the other processes already described ; the second set 

 are irregularly knob-shaped or pyriform, their investment is no 

 thinner than that of the surrounding parts, and there are no definite 

 ducts ; their whole surface is merely covered with closely-packed, 

 fine hairs, altogether similar to those found over the whole of the 

 carapace. The cavity of the process is filled with a number of 

 small, spindle-shaped cells not unlike those found in the first pair 

 of antennas, and continued into processes which are more distinctly 

 seen in the stalk of the pyriform enlargement ; it can only be said 

 that they are apparently nerve-fibres. 



The most striking portions of the muscular system are the dorsal 

 and ventral longitudinal cords, some of which extend along the 

 whole length of the body, while others are attached to different 

 regions ; the muscles for the limbs, which are often very well de- 

 veloped, arise from the sides or back of the carapace, while the 

 separate joints are moved on one another by special muscles ; other 

 bundles are connected with the digestive tract, and serve to compress 

 or enlarge its lumen. 



