50 



LEPADID.E. 



ganglia (e), which are not united by any transverse com- 

 missure. From the opposite ends of these two ganglia 

 smaller nerves run, and, bending inwards at right angles, 

 enter, beyond the middle, an elongated (r), almost black, 

 eye, composed of two eyes united together. Although in 

 outline the eye appears single, two lenses can be distinctly 

 seen at the end, directed upwards and towards the 

 ganglia ; two pigment-capsules can also be distinguished ; 

 these are deep and cup-formed, and of a dark reddish- 

 purple. The following measurements will show the pro- 

 portions of the parts in a specimen of the Lepas fascicularis 

 having a capitulum -^ths of an inch in length. 



Double eye {Jjg§* * \ \ 

 Diameter of single lens . 

 Ophthalmic ganglion {^ } ; 



26 



BooB 



13 



BoC<5 

 6 



Bono 



Bo5(5 

 n 



BooO" 



Supra-cesophageal ganglion, " 



transverse or longest axis > 



of both together 

 Supra-cesophageal ganglion, "I 



longitudinal axis of . .J 

 Infra-cesophageal ganglion, 1 



transverse axis of .J 



Infra-cesophageal ganglion, \ 



longitudinal axis of . . J 



12fl 



Boo~0" 



45 



BooU 



120 



B003 



114 



Bo0(5 



In Conclioderma aurita the ophthalmic ganglia are 

 much smaller, and nearer to the supra-cesophageal gan- 

 glion, than in L. fascicularis. In Alepas cornuta the 

 ophthalmic chords run towards each other from the two 

 distant and separate supra-cesophageal ganglia ; and the 

 ophthalmic ganglia, (instead of being quite separate, as in 

 L. fascicularis,) are united by their front ends, and the 

 two eyes instead of standing some way in front, with 

 nerves running to them, are embedded on the double oph- 

 thalmic ganglion ; the pigment-capsules here, also, have 

 the shape of mere saucers, and are joined back to back, 

 with the two lenses projecting far out of them. In neither 

 sex of Ibla could I perceive that the eye was double. In 

 Pollicipes spinosus the ophthalmic ganglion stands in 

 front of the single supra-cesophageal ganglion, and shows 

 no signs of being formed of a lateral pair j the eyes them- 

 selves, however, differently from, in all the foregoing cases, 

 are, though approximate, quite distinct. In Pollicipes 



