854 Analysis of Scientific Books and Memoirs. 



Sth, Mounting for dissections, &c. 



9th, Mounting the diamond and sapphire microscopes for opaque objects. 



10th, The Amician Catadioptric Engiscope. 



Chap. VII. — On the larva of a species of British Hydrophilus. 



The various subjects which occupy these chapters are treated with 

 great perspicuity, and with much practical knowledge of the microscope ; 

 and the descriptions are illustrated with three plates, one of which is finely 

 coloured. 



It would be impossible to convey to the reader any idea of this part of 

 the work ; but we shall make an extract from the description of the hy- 

 drophilus, which forms the subject of the Seventh Chapter. 



*' In examining the peculiarities of the structure and hnbits of this 

 larva, the faculty which most attracts our attention is its ferocious and sa- 

 vage disposition, and the fitness of its organs for the exercise of its raven- 

 ous propensities. It may be expressly asserted, that no species of larva is 

 known that is provided with weapons of destruction so powerful, so nu- 

 merous, and well adapted to their end, as those which this creature pos- 

 sesses. It is on this account that it has been popularly called the Water 

 Devil. Its size is but little inferior to that of the larva of any of the Bri- 

 tish Coleoptera, as it measures, when arrived at maturity, an inch and 

 a-half in length, while the superior strength and courage manifested in its 

 attacks on small fish, and other animals larger than itself, is truly sur- 

 prising. 



About the later end of April, and during the month of May, small nests 

 of these insects are often found floating among the weeds and water plants 

 in stagnant pools, and are frequently taken in the nets of those who are 

 searching for the early species of animalcules. They are in the form of 

 balls, of a dusky white colour, and a silky texture, and have each a small 

 stem of the same nature as the rest, by means of which it is attached to 

 the roots or stalks of reeds at the bottom of the water. In this situation 

 it remains during the winter, and is then effectually preserved from the 

 eflfects of intense cold. Early in the spring, the stem or cable to which 

 we have referred, is detached from the reeds, by the winds which at that 

 time prevail, and the nest rises to the surface of the water, and there floating 

 imbibes the genial influence of the sun. These nests may be taken and 

 placed in a basin of water, and, as the season advances, hatched by the heat 

 of the sun. On the larvae leaving the nest, which they accora})lish by 

 gnawing a hole in the side, the infant larva immediately descends to the 

 bottom of the vessel with its jaws extended in quest of prey, and eagerly 

 devours all the small aquatic insects that are within its reach ; if, however, 

 there is a scarcity of food in the immediate neighbourhood of the nest, 

 the larvae of the same brood may be seen to attack and devour each other. 



In its infant state this larva is very transparent ; hence its internal 

 structure may be clearly distinguished. The circulation along the prin- 

 cipal artery on each side the body can be distinctly observed, together 

 with the violent alternate motion of the vermiform body near the lower 

 extremity. 



