100 



probable, owing to the layers of tbe flattened cells 

 with fibrils and prominent walls that the appearance 

 of a membrane, called by Patten the suspensory ligament, 

 arose. No definite membrane can be seen by Schreiner 

 or myself. 



The lens lies suspended in a space which has been 

 termed a blood sinus, as blood corpuscles are occasionally 

 found. This space, which is situated between the retina 

 and the lens, like the chamber in the vertebrate eye con- 

 taining the "vitreous humour," does not appear to have 

 any connection with the lacunae of the eye stalk. I have 

 fovmd blood corpuscles only present in very few out of a 

 great many sections, and these were probably abnormal 

 occurrences due to fixation only, and the space cannot, 

 therefore, be looked upon as a blood sinus. 



The Septum. — The portion of the optic vesicle con- 

 taining the retina is separated from the lens chamber by 

 a membrane which runs completely across the eye. This 

 is the Septal Membrane (fig. 29, Sep.). Commonly the 

 retinal surface of the lens lies against it. Patten, however, 

 considers it a support for the lens to which it is actually 

 attached, and, further, that it plays the part of an elastic 

 cushion elevating the lens when it has been pulled in by 

 contraction of muscle fibres. 



Owing to the retina being pulled away from its under- 

 lying layers in sections, the septum comes perhaps to 

 touch the lens, but in the natural conditions the lens and 

 septum are not attached, and the latter can thus not act as 

 an elevator. Moreover, the whole appearance of the eye 

 and its reactions to stimuli render it extremely improbable 

 that it possesses any means of accommodation or focussing. 



The septum in the adult appears structureless, 

 thickest in the middle, where it is perforated by the 

 outer branch of the optic nerve. At this place the septum 



