REPORT ON THE SPHENISCID^. 167 



Variations in the Sciatic Plexus. — In all the species examined, with the exceptions 

 of Eudyptes chrysocome from Tristan, Spheniscus mirior, and Ap)tenodytes longirostris, 

 the ninth, tenth, and eleventh lumbo-sacral nerves pass outwards together, and have no 

 connection with the sciatic plexus. In Eudyptes chrysocome from Tristan, however, the 

 ninth nerve unites with the preceding nerves to form the sciatic plexus. In Ap>tenodytes, 

 again, only a portion of the ninth nerve enters the sciatic plexus, the remaining portion 

 being distributed along with the tenth and eleventh nerves. In Spheniscus minor a 

 portion of the eighth nerve also enters the sciatic plexus, its remaining portion and 

 the whole of the ninth being distributed along with the tenth and eleventh lumbo-sacral 

 nerves. 



Coccygeal Nerves. 



The coccygeal nerves escape from the spinal canal between the moveable coccygeal 

 vertebrae. Of them I could only distinguish four, although, seeing that the moveable 

 coccygeal vertebrae are eight in number, it appears probable that there may have 

 been seven coccygeal nerves. However this may be, the coccygeal, together with 

 the twelfth and thirteenth lumbo-sacral nerves, form long slender branches, which 

 pass backwards parallel to one another, and freely communicate by means of numerous 

 cross branches. In this way a sort of plexus is formed, which, occupying the inferior 

 surface of the caudal vertebrae, is for the most part concealed by the depressor caudaj 

 muscle of the same side. Escaping along the outer border of the depressor caudse muscle, 

 the slender trunks of these nerves pass backwards to be distributed partly to the muscles 

 of the tail, and partly to the skin of that region. 



In Sphenisctis minor I was able to distinguish five separate coccygeal nerves. 



THE SYMPATHETIC NERVE. 

 The principal cord of the sympathetic system of nerves is arranged in the Penguins 

 as in other birds. In the neck it accompanies the vertebral artery through the osseous 

 canal formed by the perforated transverse processes of the cervical vertebrae. The ramifi- 

 cations of this system of nerves I was unable to trace. 



ORGANS OF SENSE. 

 The Eye and its Appendages. 



The Muscles of the Eye-lids. — Both eyelids of the Penguins are provided with 

 muscles, by the joint action of which the aperture between them is enlarged. 



The elevator of the upper eyelid consists of a broad, flat, but very thin plate of mus- 

 cular fibres which arise from the fascia covering the orbital surface of the insertion of 

 the ocular muscles. The fibres pass transversely outwards, and are inserted into the 

 deeper surface of the upper eyelid. By the contraction of these fibres the upper eyelid 

 is raised. 



