ElMfiRtOLOGlCAL. 
Gen. Sub. 53 
Influence of gravity : Confirmation of Pfliiger’s results. With great 
regularity a simple turning of the fixed ovum through 180° is followed 
by the production of a double embryo ; Sciiultze (495). 
Formation of gastrula: The cells of the blastula, whose specific 
gravity has been decreasing, are in contact internally with fluid more 
dilute than that externally, hence a condition of invagination. In 
diluted sea-water there is a tendency to the reverse ; Loeb (815, 
316). 
Isolated blastomeres of Medusae : A fraction as small as T Vth will 
develop like an entire ovum. The early cleavages seem to be quantita- 
tive not qualitative ; Zoja (595). 
Development of isolated blastomeres of Medusae and other organisms ; 
Zoja (596), Roux (469). 
Development of blastomeres of Ascidians ; Driescii (128). 
Experiments in puncturing frog’s eggs ; Endres (144). 
Ova protected by phagocytosis and excretion. Bacterial diseases 
cannot be transmitted either by ovum or spermatozoon ; Francotte 
(169). 
Influence of pressure on cleavage : Results of experiment applied to 
the elucidation of normal cleavage ; the succession of events in the 
development of the blastosphere of Synapta is influenced by the pressure 
of the egg membrane on the blastomeres, and by their mutual pressure ; 
Braem (61). 
Influence of temperature on hen’s eggs : The optimum temperature is 
38° 0. during early days of incubation. On each side of this the embryo 
increases in susceptibility to injurious influences, e.g alcoholic vapour ; 
FriRri (151). 
Influence of vibrations; Fejr£ (152). — Influence of mercurial vapours; 
Feri£ (153). 
Experiments on frog ova : Temperatures above 25° C. affect the ova 
injuriously, especially the vegetative part. Partial embryos may result. 
Weak salt solutions 3 : 500 affect the formation of blastopore, and the 
development of brain, &c. ; Hertwig (236). 
Cytotropism : Segmented ova of frog were teazed ; the isolated cells 
exhibited gliding movements and sometimes pseudopodia ; a plasmodial 
aggregate may be formed ; besides the change of position there is 
change of form ; the phenomena are not merely physical ; Roux 
(468). 
Laws of cleavage : In Limax there is an alternation in the direction 
of the spirals of cleavage in successive generations of cells ; Kofoid 
(281). 
The production of half-embryos ; Roux (465). 
Influence of rarefied air on the development of the chick ; Giacomini 
(185, 186). 
Orientation of frog’s ovum; Morgan & Tsuda (378). 
Ova of Arbacia segmenting under pressure, exhibit fusion of cells, and 
go back ; Graf (196). 
1894. [vol. xxxi.] b 8 
