THE HYDRA. 71 



FIG. XXI. The ovum of Fig. XVII., liberated under geiitle pressure. D. 2. 



FIG. XXII. Two ripe spermatozoa from the same. F. 4. 



FIG. XXIII. The ovum, at a late stage of segmentation, still enveloped in its 

 membranes. D. 2. 



The sexual reproduction of Hydra has long been a vexed question; the last contribution 

 to the subject is that of Korotneff (92). 





al. Digestive (body) cavity. 



bl. Mouth (blastopore). 



e. Cilia. 



d. Chlorophyll-forming bodies. 



cl'. Chlorophyll corpuscles. 



c.l. Supporting lamella. 



c.p. Kleinenberg's fibres. 



(/. An ingested diatom. 



ec. Ectoderm. 



ec'. Larger ectoderm cells. 



cc". Smaller ectoderm (interstitial) cells. 



en. Endoderm. 



e.s. Egg shell. 



/. So-called foot. 



ij.t. Germinal spots. 



!/.r. Germinal vesicle. 



li/i. Hypostomo. 



nc. Nucleus. 



ne. Nematocysts (various). 



ne'. Larger uematocysts, before rupture. 



or. Ovary. 



UK'. Ovum. 



jis. Pseudopodia. 



f Tentacles. 



('. Young (last formed) tentuclus. 



t. Testis. 



vc. Vacuole. 



cc'. Amyloid vacuole of endoderm cell. 



ij.ij. Yolk granules. 



