12 ARTHTTR DENDY. 



connected witli the sensory cells of the retina by delicate 

 strands of tissue which traverse the lumen of the optic vesicle. 

 This is very evident in the case of Geotria also, as indicated 

 on the left-hand, side of fig. 7. This figure, however, re})re- 

 sents a section of an eye which has been somewhat abnormally 

 distended in the processes of preparation, and in which, con- 

 sequently, most of the delicate connecting strands have been 

 ruptured; in other cases, where the pellucida has not become 

 artificially arched, outwards, all the projections of its inner 

 surface are connected in this manner with the retina, and. 

 the general direction of the connecting strands is vertical. 

 The strands themselves appear to be formed by outgrowth of 

 the inner ends of the long columnar cells of the pellucida, 

 which become attached to the knobs of the retinal sense cells. 

 In all cases which I have observed, however, they appear to 

 branch and form an irregular network (fig, 7), which may be 

 partially due to artificial entanglement. Entangled, as it 

 were, in the meshes of this network, one finds numerous small 

 nuclei, which often stain very darkly and exhibit a character- 

 istic shrivelled appearance as if undergoing degeneration. 

 Sometimes, also, one finds an irregular mass of almost homo- 

 geneous material with nuclei adhering to its surface — probably 

 identical with the " syncytial mass " described and figured by 

 Studnicka in Petromyzon fluviatilis, but, in my opinion, 

 an artifact due to coagulation and entanglement. Such a 

 mass is shown in the middle of the optic vesicle in fig. 7. 

 Studnicka regards the " plasmatischen Netze und Syncytien" 

 as representing the remains of a '^corpus vitreura," but this 

 appears to be a mere question of terminology, and it is 

 extremely doubtful whether it is desirable to apply the term 

 " corpus vitreum " to such very definite structures as the 

 protoplasmic strands which connect the pellucida with the 

 retina, although it is quite possible that these may be im- 

 bedded in a " corpus vitreum " during life. It seems probable 

 that the function of these connecting threads may be to afford 

 support to the freely projecting knobs of the sense cells by 

 attaching them to the pellucida. 



