440 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



just such cases make it seem probable that our descendants will 

 learn quicker what we knew well; will execute easier what we accom- 

 plished with great effort; will be able to withstand what injured us 

 almost to the point of death. In a word, where we sought, there 

 they will find; where we began, there they will accomplish; and where 

 we are still fighting with uncertain results, there they will be victo- 

 rious. 



EXPLANATION OF PLATE FIGURES. 



Fig. 1. — Slipper animalacule (Paramaecium). — 1, normal, more enlarged, and less 

 schematic; la, offspring resulting by fission from an example which has been 

 distorted by hunger, every time one offspring with a hornlike process; 16, incom- 

 plete fission the fission products remain attached to each other. (After Jennings 

 and McClendon, from Przibram's Experimentalzoologie, vol. 3.) 



Fig. 2. — Aeolosoma hemprichii. — Upper left-hand figure normal worm, T, budding; 

 a, a worm in which the end was cut off, in spite of which a new worm is bud- 

 ding in aT; b, biid fused with the stem part, in feT, producing, in spite of this, 

 another normal bud. (After Stole, from Przibram's Experimentalzoologie, vol. 3.) 



Fig. 3. — Lumbriculus. — Above normal worm AH anterior, Bo, posterior segments, 

 which are cut away and produce tails, a, b; in a and b these separated tails have 

 acquired new heads; in a and b the latter have each grown another set of tails. 

 (After Morgulis, from Przibram's Experimentalzoologie, vol. 3.) 



Fig. 4. — The approach of the Salinecrustacean (Artemia) (1) to Branchipus (2). 

 When the saline contents of mediimi are reduced, la-/, gradations of the pos- 

 terior segment of the abdomen of the Salinecrustacean; 2g, posterior segment of 

 the abdomen of Branchipus. (After Schmankewitsch, from Przibram's Experi- 

 mentalzoologie, vol. 3.) 



Fig. 5. — A water flea (Hyalodaphnia). To the left high, right low helmed females, 

 with eggs in the brood pouch. In the middle are the results of three experi- 

 ments (1-111), represented by sketches of the head outline; aa, females; bb, 

 young. (After Ostwald, from Przibram's Experimentalzoologie, vol. 3.) 



Fig. 6. — Vital staining in the moth Tineola biselliella. — A caterpillar stained with 

 sudan red. B, colored egg, deposited by a moth developed from the stained 

 catei-pillar; b, normal, colorless egg. (After Sitowski, from Przibram's Experi- 

 mentalzoologie, vol. 3.) 



Fig. 7.— Changing the small willow leaf beetle (Phratora vitellinas) from a smooth 

 leaf (^4) to a strongly woolly willow leaf (a). In B most of the eggs have been 

 deposited upon the original food plant (above); in b the eggs have been placed 

 upon the new food plant. Analog in C, c, D, in which an increasing number 

 of eggs are deposited upon the new food plant. The numerical difference in 

 the number of the eggs deposited is indicated by the number of circles alongside 

 of the twigs. To the right below is the beetle. (After Schroder, from Przibram's 

 Experimentalzoologie, vol. 3.) 



Fig. 8. — Development and metamorphosis of an ordinary frog, a, freshly deposited 

 eggs; b, with swollen capsule; c, before hatching; d, freshly hatched larva; e, 

 with external gills; /, external gills retrogressing; g, h, footless larva with internal 

 gills; i, larva with hind legs; k, with the beginning of front legs; I, with all four 

 legs; m, after discarding the horny jaw and almost complete shriveling of the 

 tail. (After Brehm.) 



Fig. 9.- — Adaptation of the midwife toad {Alyles obstetricans) . 2, normal develop- 

 ment; a, egg; b, freshly hatched larva; c, two-legged d four-legged larva; e, 

 newly developed toad; o, lung of larva; e, lung of complete toad. 3, develop- 

 ment from "giant eggs"; a, egg; b, newly hatched larva; C, newly hatched off- 



