Anatomy of Stephanoceros Eichhornii. 7 



itself a central refracting medium." He is uncertain 

 " whether they incline to the simple or compound type ; they 

 are eminently calculated to fulfil the purposes they are required 

 to serve, in simply conveying light, though not the perception 

 of objects to the brain, for they possess no choroid." 



I must confess that on the strength of the foregoing remarks 

 my curiosity was considerably aroused. I examined my 

 sections taken through the region where, in the liviug animal, 

 I had seen these red bodies without finding any structure at 

 all agreeing with a visual organ. All that I could find were 

 two spherical bodies, one being placed more superficially than 

 the other, of a chitinous nature, and which, when examined 

 with a dark-ground illumination, resembled in every way the 

 so-called eye. The firmer and more external one is imbedded 

 in a homogeneous structureless mass, which presents at some 

 points certain lines of no definite outline {vide PI. II. fig. 6). 

 The organ appears to be composed of two parts, an outer ring 

 of a highly refractive nature, enclosing a central opaque mass. 

 The second eye is placed deeper in the tissues of the animal, 

 and the homogeneous mass in which it is placed does not 

 appear to possess the firmness noticed in its fellow. The 

 organ is composed of a less dense material, splinters readily 

 under the knife, and shows in consequence its structure 

 admirably. These organs are not present in all my sections. 

 As to their use to the animal I am unable to offer at present 

 any suggestion ; but I think one may safely assume they are 

 not visual organs. 



Ovary and Development. — The remarks I have to make 

 under this heading are few, but still of considerable interest. 

 The earliest writer, so far as I can find, who has touched upon 

 the origin of the envelope surrounding the ovum is Prof. 

 Huxley. He says (7), " The ova are developed thus : — One 

 of the vesicles increases in size, and reddish elementary 

 granules appear in the homogeneous substance round it. This 

 accumulation increases until the ovum stands out from the sur- 

 face of the ovary ; but invested by its membrane which, as 

 the ovum becomes pinched off as it were, takes the place of a 

 vitellary membrane." 



Dr. Zacharias (loc. cit.) says, " The process of separation 

 is so effected that a portion of the enveloping membrane of 

 the ovary is separated with it and transferred to the ovum, so 

 that the embryo in its development lies in a completely closed 

 hyaline vesicle, which, from its origin and function, is to be 

 regarded as a real uterus." With these remarks my investi- 

 gations entirely agree; but, as both the above-mentioned 

 authors obtained their views by means of optical sections, I 



