early days of spring, when the sudden atmospheric changes are very detrimental, and frequently fatal to the growing caterpillars. * * * * * =The Natural History of the Eel.= According to the reports of shad fishermen, the chief enemy of the shad is the eel, which not only follows that fish up the streams and devours the spawn, but often attacks the shad after they are caught in the nets. Entering the shad at the gill openings the eels suck out the spawn and entrails, and leave the fish perfectly clean. The finest and fattest shad are the ones selected. It is a curious circumstance that of a fish so well known as the eel so many of its life habits should be in dispute. An animated discussion has been going on in Germany quite recently with regard to the natural history of this fish, and in a late number of a scientific journal the following points are set down as pretty well substantiated. Though a fresh water fish which passes the greater part of its life in rivers, the eel spawns in the sea. That it is viviparous is extremely improbable. The eel found in the upper waters of rivers is almost always female. At the age of four years it goes down to the sea to spawn and never returns to fresh water. The spawning process is somehow dangerous to the eel, thousands being found dead near the mouths of rivers, with their ovaries empty. The descent of the fish to the sea does not appear to take place at any definite period, but is probably dependent on the season for spawning. The male is always much smaller than the female, and never exceeds half a yard in length. The males never ascend to the head waters of rivers, but keep continually in the sea or in the lower reaches of the river. Nothing is definitely known about the spawning season, though it is probable that the eggs are deposited in the sea not far from the mouths of rivers. * * * * * [Illustration: THE PARIS EXHIBITION.--A SKETCH IN THE PARK.] * * * * * [Illustration: "Scientific American." In Gothic script] Established 1845. MUNN & CO., Editors and Proprietors. PUBLISHED WEEKLY AT NO. 37 ARK ROW, NEW YORK. ====================================================================== O. D. MUNN. A. E. BEACH. ====================================================================== =TERMS FOR THE SCIENTIFIC AMERICAN.= One copy, one year, postage included..........................$3.20 One copy, six months, postage included........................$1.60 =Clubs.=--One extra copy of THE SCIENTIFIC AMERICAN will be supplied gratis for every club of five subscribers at $3.20 each; additional copies at same proportionate rate. Postage prepaid.