CTanhabt 16, 1914] 



SCIENCE 



107 



lishing Company. 1913. Pp. viii + 210; 1 



plate; 101 figures in text. Price, ninety 



cents. 



This little volume presents in an interesting 

 manner those facts concerning rocks which 

 are of interest to the student of general geol- 

 ogy. The author has in mind a pocket manual 

 which may be of service in the field. The 

 treatment is from the standpoint of the macro- 

 scopic properties of rocks and is thoroughly 

 modern. The book is well printed. The il- 

 lustrations are excellent. 



Edward H. Kiiaus 



MlNERALOGICAl LABORATORY, 



University of Michigan 



SPECIAL ABTICLES 



THE OULTIVATION OF TISSUES FROM THE FROO 



In a series of experiments on the culture in 

 vitro of tissues of the frog it was found that 

 several kinds of tissues show a marked out- 

 growth after being kept for a few days in 

 lymph or plasma. Small pieces of the tissues 

 were mounted according to the usual method 

 in hanging drops of the culture medium and 

 sealed with vaseline in hollow slides. Cells 

 may remain alive under these conditions for 

 several weeks. 



Spleen, bone-marrow and pseudothyroid give 

 rise to a fringe of outwandering cells resem- 

 bling leucocytes which extend farther and 

 farther into the surrounding medium. Larger 

 connective tissue cells wander out later, and 

 both types of cells exhibit amoeboid changes. 

 Small pieces of tissue may almost entirely dis- 

 integrate into wandering cells. 



The epithelial cells of the skin extend gen- 

 erally as a broad thin sheet of tissue. The cells 

 move out in contact with the cover slip or the 

 lower surface of the drop. Individual cells of 

 the epidermis may become isolated and creep 

 out alone, but there is a marked tendency for 

 the cells to keep together in a continuous mem- 

 brane. In a previous paper on the movements 

 of the ectodermic epithelium of amphibian 

 larvae^ it was shown that the ectoderm cells 

 actively creep out by an amosboid movement of 



lUniv. of Calif. Pubs. Zool., 1913. 



the very thin and transparent protoplasm of 

 their free borders. The method by which 

 sheets of epithelium extend in the adult frog 

 is essentially the same as in the embryo or 

 larva. 



In several cases black pigment cells were 

 seen to isolate themselves and wander out along 

 the cover slip or lower surface film of the drop. 

 In some cases, especially in the smaller pig- 

 ment cells, the changes in form were fairly 

 rapid. Pseudopods were thrust out and re- 

 tracted very much as in the common amoeba, 

 and in some instances the cells were seen to 

 migrate nearly across the field of the micro- 

 scope. The processes of the pigment cells of 

 the adult, unlike those of the larvse, may be 

 nearly transparent, and they usually are so 

 when first formed; frequently, however, they 

 are very sooa invaded by pigment granules. 

 Outwandering cells may show branching proc- 

 esses characteristic of the expanded melano- 

 phores of the frog's skin. The change in form 

 of the pigmented mass within the cell is due 

 in part to changes in the outline of the whole 

 cell and in part to the flowing back and forth 

 of pigment granules within the ceU processes. 

 There is a measure of truth, therefore, in both 

 the rival theories of the changes of the chro- 

 matophores in the skin of the frog. 



In some preparations the peritoneal epithe- 

 lium wandered out in the form of a sheet of 

 tissue considerably greater in area than the 

 original preparation. For the most part the 

 extension consisted of flattened cells arranged 

 in a single layer and showing a hexagonal con- 

 tour like the cells of the shed cuticle. Many 

 of these cells were furnished with cilia which 

 beat actively for two weeks. The ciliated cells 

 frequently became amreboid and wandered free 

 from the rest, sending out fine processes several 

 times the original diameter of the cell. Some- 

 times the processes branched repeatedly. One 

 would not suspect these cells to be derived from 

 ciliated epithelium were it not for their tuft of 

 beating cilia, and the fact that one can actually 

 observe their transformations. Follicle cells 

 of the testis may creep out and give the appear- 

 ance of giant amoebse. 

 Fuller details of the behavior of Tarioua 



