4. From the fertile ova, as the fish increase in size, something like a shell is separated; this is the membrane which envelopes the ovum and the embryo fish. As soon as the seminal fluid is mixed with the ova a glutinous matter is formed, which fastens them to the roots or other substance on which they are deposited. The male watches over the place where the greatest number of ova are deposited, and the female departs as soon as she has spawned. The development of the ovum of the glanis proceeds the most slowly, for the male remains by them for forty or fifty days, in order that they may not be devoured by fish chancing to come that way. 5. Next to this is the cyprinus. The ova, however, of these which are preserved escape very quickly. The development in some of the small fish takes place on the third day, and the ova upon which the seminal fluid has fallen begin to increase on the same day, or shortly afterwards. The ova of the glanis become as large as the seed of the orobus. Those of the cyprinus and that class, about the size of millet. The ova of these fish are produced and developed in this manner. 6. The chalcis assembles in great numbers to deposit its ova in deep water. The fish which is called tilon deposits its ova near the shore, in sheltered places; this fish also is gregarious. The cyprinus, balerus, and all others, so to say, hasten into shallow water to deposit their ova, and thirteen or fourteen males often follow a single female, and when the female has deposited her ova and departed, the males that follow her sprinkle their semen upon them. The majority of the ova are lost, for the female scatters them abroad as she is moving forward, unless they fall upon any substance, and are not carried away by the stream. None of them, except the glanis, watch their ova, unless the cyprinus meets with them in great numbers, when, they say, that this fish watches them. 7. All the male fish have semen, except the eel, and this one has neither semen nor ova. The cestreus migrates from the sea into lakes and rivers; the eel, on the contrary, leaves them for the sea. Most fish, therefore, as I observed, proceed from ova. CHAPTER XIV.