366 



INVEETEBEATA 



CHAP. 



reacquire their cavities, and then the kidneys become fused together 

 in the mid-ventral line ; this fusion is characteristic of Loligo, and 



does not occur in 

 Sepia. 



By ' far the most 

 complicated 



organ 



n 



Fie. 298. Two early stages in the 

 eye of L<>li<i<> rulijiiris seen in 

 ( After Lankester, from l!;ilt'our. ) 



of, eye-cup; r, rudiment of retina. 



levelopment of the 



transverse section. 



the Cephalopod is the 

 eye, the general features 

 of the development of 

 which have already been 

 described. Some details 

 may now be added. As 

 soon as the primary 

 eye pit closes the inner 

 segment of the lens 

 begins to be formed. 



O 



It first appears as a 

 thin cuticle spreading 



w 



y fx 



Fit;. 299. Sections through the developing eyes of young cuttle-fish to show the 



development of the leus. (After Faussek.) 



A, Section through the eye of Lulirjn rn/i/nri*. U, Section through tlio eye of .sv^/Y; oflirinnlin. c.e-ii, 

 Ifii^'c- cells (if (he corpus epitheliale ; r.c/i', sni.-ill cells of the jiei iphci-y nC I lie cm pus cpithcli;ile which 

 grow over the larger cells .-mil secrete the lilnes nl' the lens ; i.l, inner segment <>t' the 1 lens ; ir, iris ; 

 ?./, lens liliics. 



over a considerable portion of the inner surface of the closed eye- 

 sac, but it becomes thickened at one point in the centre, and 



