ZOOLOGY AND BOTANY, MIOROSCOPY, ETC. 191 



amining the larvae of Pelohates fuscus. He found in the posterior region 

 of the roof of the pharyngeal Civity (from ceratohyal to cesophagus), a 

 highly developed system of multicellular glands differing from all other 

 known multicellular glands of vertebrate animals in that they are not 

 imbedded in the connective-tissue layer, but are entirely limited to the 

 epithelium, which at that point is fourfold. Each gland is in shape like 

 a more or less broad, round pumpkin flattened in the main axis. The 

 flattened basal surface is seated on the connective-tissue layer, while the 

 upper surface reaches to the surface of the epithelium. The cells which 

 form the glands consist of longitudinally extended prisms closely 

 pressed together. The glands form a belt of about 2 mm. in breadth. 

 At the edges of this belt they are comparatively far apart, but in the 

 middle they stand so close together that their edges touch. 



Factors in the Evolution of Cave Animals.* — Prof. A. S. Packard, 

 in the advance sheets of an essay on the cave animals of North America, 

 contends that the phrase " Natural Selection " expresses rather the 

 result of a series of causes than a vei-a causa in itself; and that the 

 constant use of such a phrase tends to obscure vision, and to prevent the 

 discovery, by observation and experiment, of the tangible, genuine, 

 efficient factors of organic evolution. He enumerates the following as 

 the most important and potent factors in the evolution of cave animals : — 

 (1) Change in environment from light, even partial, to twilight or total 

 darkness, involving diminution of food, and compensating for the loss of 

 certain organs by the hypertrophy of others. (2) Disuse of certain 

 organs. (3) Adaptation, enabling the more plastic forms to survive and 

 perpetuate their stock. (4) Isolation, preventing intercrossing with out- 

 of-door forms, thus insuring the permanence of the new varieties, species, 

 or genera. (5) Heredity, operating to secure the permanence of the 

 newly originated forms, as long as the physical conditions remain the 

 same. Prof. Packard gives illustrations of the action of these factors, 

 citing facts both new and old, and argues on behalf of what he calls 

 " Neo-Lamarckism." 



/3. Histoloffy-t 



Division of Red Blood-corpuscles in Amphibia.^ — Dr. L. Torok has 

 investigated the phenomena of cell-division in the red blood-corpuscles 

 of Amphibians {Salamandra maculata), in regard to which Flemming and 

 others had previously noticed certain deviations from the normal type. 

 In the resting stage the chromatin is present in relatively greater 

 abundance and denser disposition than in the resting nuclei of other 

 kinds of cells. The large size of the subsequent nuclear figures is inter- 

 preted as due partly to the dissolution of the filaments and strands from 

 their previously close arrangement, partly to a change of the chromatin 

 into a less dense state. The processes of division are described in detail 

 — the formation of the close coil, of the loose coil, of the loops and the 

 aster ; the longitudinal division of the filaments in the loose coil and 

 star-figure, or even in the first stage ; the disappearance of the nuclear 

 membrane in the loose coil and the consequent mingling of cell-proto- 



* Amer. Natural.. 1888, pp. 808-21, 



t TLis section is limited to papers relating to Cells and Fibres. 



i Arch. f. Mikr. Anal., xxxii. (1888) pp. 603-13 (1 pi.). 



