372 SUMMARY OF CURRENT RESEARCHES RELATING TO 



these constrictecl off periblast elements as cells, and not nuclei. Sections 

 made at a later date confirmed his observations on the living objects. 



Only three layers of cells at most were seen round the blastodisc 

 margin. On sections, thirty-two hours after fertilization, there was seen 

 below the blastodisc a single layer of cells, distinctly flattened and stretch- 

 ing like a flat epithelium from one margin to the other. The component 

 cells had distinct nuclei, many somewhat larger and more spherical than 

 those of the blastoderm. From the section Dr. List inferred that the con- 

 striction of periblast cells took place not only outwards, but also inwards 

 below the blastoderm to form the layer just noted. How long the external 

 budding off goes on was not determined. Without regarding the available 

 data as adequate, the author is inclined to believe that the hypoblast arises 

 from the periblast. 



Formation of Double Monsters.* — M. C. Dareste has a note on recent 

 researches on the mode of formation of double monsters. He allows that 

 there are double monsters as to which his explanation by the formation of 

 two embryonic bodies from a single cicatricula will not apply ; these, 

 which have been inexactly called monsters by lateral union, are only 

 partially double ; they are very rare among birds, but are pretty fx-equent 

 among fishes after artificial fecundation. Here even there is initial 

 duality, but the fusion takes place very early, even, he thinks, before seg- 

 mentation. And ho suggests that an explanation is to be found in the 

 history of the process of fecundation ; if the single fertilizing spermatozoon 

 forms the male nucleus, would not two spermatozoa give rise to two male 

 nuclei, or, in other words, to two foci of embryonic formation ? 



/3. Histology, t 



Chemistry of Cell-nucleus. $ — Herr A. Kossel finds that when yolk 

 nuclein is broken up by boiling dilute acids it does not fonn guanin and 

 hypoxauthin as docs nuclear nuclein. Adeniu is a new base formed in 

 the decomposition of the nuclei of the pancreatic gland, and appears as an 

 intermediate product in the formation of hypoxauthin, into which it passes 

 under the action of nitric acid ; it has been found in numerous animal and 

 vegetable cells. 



Death of Muscles. § — After death, when the muscles have ceased to 

 respond to electrical or mechanical stimulus, there still remains a certain 

 irritability. It is still possible to provoke contractions of final agony, which 

 end finally in a particular form of rigidity. M. C. Eouget has studied 

 these last manifestations of life in muscle. A small detached portion was 

 placed on an object-glass in a droj) of 6 per cent, salt solution, and the 

 fibres teased apart. The stretched fibres contract like caoutchouc when the 

 tension is relaxed ; they twist variously when freed, with greatest rapidity 

 in birds, mammals, and fishes among Vertebrates, and in Orthoptera and 

 Crustacea among Invertebrates. The most leisurely movements were ob- 

 served in HydropMlus. 



At the free extremity of the fibres a local contraction takes place, and 

 similarly at all points where the fibres have been pressed or lacerated. In 

 Arthropods these gradually encroach on the rest of the fibre. In frogs 

 and lizards, after the appearance of the pads of contractions, ruptures occur, 



* Comptes Rendus, civ. (1887) pp. 715-7. 



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



X Zeitschr. f. Physiol. Chemic, x. (1886). See Bot. Centralbl., xxix. (1887) p. 39. 



§ Compter Eeudus, civ. (1887) pp. 1017-20. 



