PROPAGATION OF HYDRA. 83 



a glandular-looking body and innumerable active particles are seen to 

 be contained. 



(188.) The conical eminences, which constitute the spermatic cap- 

 sules, appear to derive their origin from the greater degree of develop- 

 ment of one or more of the superficial cells in the vicinity of the base 

 of the arms. These capsules sometimes occur in considerable numbers, 

 as from eight to sixteen, on the brown polyp ; but in the green species 



Fig. 40. 



Oviparous reproduction of Hydra viridis. 1. Body of Hydra magnified : a, the ovum contained 

 in the ovigerous capsule sprouting from the side of the polyp ; 6, 6, spermatic capsules. 2. Mature 

 ovum of Hydra crushed, its contents escaping. 3. Spermatic capsule broken by pressure, showing 

 the contained spermatozoa. 



only two or three are generally seen, placed on opposite sides of the 

 body, and invariably situated somewhere in the vicinity of the oral 

 extremity (fig. 40, 1, 6 6). The interior of the capsules has a slightly 

 ribbed or striated appearance ; and at the summit a small aperture is 

 sometimes perceptible, through which, when the development is com- 

 plete, the spermatic filaments are observed to issue. On breaking up 

 the capsule, under the microscope, large numbers of these filaments are 

 seen united in bundles by their minute globular heads, the filamentous 

 part being free, and vibrating with great rapidity in the manner which 

 is known to be characteristic of these bodies in all animals (fig. 40, 3) . 

 These| spermatic capsules were observed by Dr. Allen Thompson* on many 

 individuals in which no ova existed. The ova are developed in the 

 lower portion of the body, which, at the time when the male apparatus 

 makes its appearance, becomes considerably enlarged, presenting an 

 opake swelling, in the interior of which an ovum makes its appearance 



* Edinburgh New Philosophical Journal, 1846. 



G2 



