94 STERELMINTHA. 



and this not on one side only of the creature, but on both ; all 

 the parts being precisely similar in the two lateral halves. 



The ovarium is not distinguishable as a distinct viscus, the 

 gems or granular-looking ova (e) being apparently diffused through 

 the parenchyma of the body around the alimentary channels. 

 From this situation the ova are taken up by two long oviducts, 

 which, turning upon themselves near the mouth, are seen to per- 

 form a long course through the anterior part of the body, until at 

 (/) they unite, and immediately expand into a capacious intestini- 

 form cavity, or uterus, (g), from which the eggs escape when 

 mature through a lateral aperture (A). 



The male or seminiferous apparatus is quite unconnected with 

 the female organs, and its structure is easily distinguishable. The 

 testicle (i) is a small pear-shaped vesicle, from which a duct may 

 be traced, which ends in a long cirrus (Ar), represented in the 

 figure as coiled up in a spiral form ; but when unrolled it is of 

 considerable length, and analogous both in structure and office 

 to the male organ of Distoma. 



(125.) We now arrive at the most perfect type of structure found 

 in the Parenchymatous Entozoa, which leads us by a gradual trans- 

 ition to the more highly organized forms which are possessed of 

 a distinct nervous apparatus. The reader will observe that in 

 all the preceding genera the alimentary canal has consisted en- 

 tirely of nutritive canals excavated in the substance of the body, 

 and unprovided with any outlet distinct from the mouth adapted 

 to the discharge of the residue of digestion. From the nature of 

 their food, indeed, we might be led to infer the reason of such a 

 structure ; for living, as these creatures do, upon juices already 

 completely animalized and prepared for the purposes of nutrition, 

 the assimilation of the materials provided for them constitutes 

 nearly the entire process of alimentation. The same con- 

 formity to one type has been also visible in the nature of the 

 reproductive system ; all the species which we have as yet ex- 

 amined, except perhaps the Planarise, having possessed indepen- 

 dent powers of propagation, either containing no visible organs 

 appropriated to the developement of the germs which they 

 produce, or possessing both an ovigerous and impregnating 

 apparatus combined in the same body. The Entozoa acantho- 

 cephala, of which we are now about to speak, will be found still 

 to exhibit a digestive system analogous in structure to that which 

 exists universally among the Sterelmintha, but in the organs 



