CATERPII.LAR AND THE MOTH
organs by means of enzymes produced in the nuclei of the cells. The fat cells thus take on the function of a stomach, converting the materials dissolved in the blood into forms that the growing tissues can assimilate. During this time the masses of fat tissue that compose the fat-body of the
"r<??>:,?.ç:?:o " :-:oE--: ?:¢.,' / e I.? ,???/" ? ? ?é?? "... " "/"" ? ? O- " .- -?-.--..:»" :e«::?.a?« ? <?çi?::.-:???: ?O Fro. ?6o. Bodies in the blood of a young pupa of the tent c?terpillar a, a free fat cell, containing large oily fat globules, and small proteid granules; b, r, fat cells in dissolution; d, froe proteid granules in the bl?ed, and e, fat globules liberat? from the disintegrating fat cells;f, bl?ed corpuscles
larva have broken up into free cells, and these cells, vacuolated with oii globules and later charged with pro- teid granules, now fill the blood. The interior of the moth pupa, or chrysalis, shortly after the larval skin is shed, contains a thick, yellow, creamy liquid. In it there may be discovered, however, the ali'mentary tract, the nervous system, and the tracheal tubes, the latter filled with air; but all these parts are so soft and delicate that they can scarcely be studied by ordinary methods of dissec?ion. The creamy pulp of the pupa's body, when examined under the microscope, is seen to consist of a clear, pale, amber-vellowish liquid full of small bodies of various sizes (.1Oig. ?6o), which give it the opaque appearance and thick consistencv. The liquid medium is the blood, or body lymph. Tl?e largest bodies in it are free fat cells (a); sma'ller ones are probably blood corpuscles (f); and the
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INSECTS
