168 THE VOYAGE OF H.M.S. CHALLENGER. 



The depressor of the lower eyelid is a powerful muscular band, the origiai of which is 

 situated on the floor of the orbit, under cover of the Harderian gland. The muscle 

 arises from the basi-sphenoid bone opposite the orbital process of the os quadratum. Its 

 fibres pass obliquely forwards and outwards, to be inserted into the lower eyelid, as well 

 as into the conjunctival membrane behind it. The origin of this muscle lies between 

 the Harderian gland and the pterygoid muscle. It acts as a depressor of the lower eyelid. 



The muscles of the third eyelid or membrana nictitans are arranged exactly as in 

 other birds. 



Such is also the case as regards the ocular muscles, the two oblique muscles arising 

 together from the anterior and internal waU of the orbital cavity, while the recti 

 muscles at their origin surround the optic foramen. 



The lachrymal gland in Eudyptes chrysocome is of a somewhat oval form, and rather 

 smaller than a garden pea. It lies in contact with the eyeball, under cover of the post- 

 orbital process. From it a single duct passes off which extends downwards and forwards, 

 to open upon the sui'face of the palpebral conjunctiva immediately behind the posterior 

 commissure of the eyelids. 



The Harderian gland is extremely large. It occupies the entire floor of the orbital 

 cavity, resting upon the upper surface of the palate bone and pterygoid muscle. Its upper 

 sui-face is in contact with the globe of the eye. The duct passes off from the anterior 

 extremity of the gland, and, winding round the inner side of the eyeball, opens upon the 

 conjunctival membrane covering the ocular surface of the membrana nictitans, opposite 

 the anterior commissure of the eyelids. Thus, in the Penguins as in other birds, there 

 are two glands in connection with the orbit, the duct of one of which opens behind and 

 the other in front of the eyeball. The secretion of both is carried off by means of the 

 lachrymal duct. 



The lachrymal duct is single throughout. It commences at an orifice situated on the 

 anterior commissure of the eyelids, and passes obliquely forwards and downwards to 

 gain the nasal fossa, where it terminates close to the orifice of the duct of the nasal gland. 

 These two ducts pass forwards parallel with one another, but while the duct of the nasal 

 gland is deeply situated, and perforates the anterior margin of the orbit before opening 

 into the nasal fossa, the lachrymal duct is superficially placed, and lies immediately under 

 cover of the skin. 



According to Owen,^ the lachrymal duct in birds commences by two apertures at the 

 nasal canthus. Such is not the case in any species of Penguin. 



The nasal gland in the Penguins is of very large size. It occupies the deep crescentic 

 groove situated on the upper surface of the skuU, close to the margin of the orbit. 

 Widest behind, the nasal gland diminishes to a point anteriorly, and from this extremity 

 of the gland the duct arises. The duct passes forwards and downwards, lying in a 



1 Anatomy of Vertebrates, vol. ii. p. 144. 



