42 SUMMARY 'OF CURRENT RESEARCHES RELATING TO 



opening out of the shortened diplotene rods along the line of cleavage, 

 so as to assume eventually the form of stretched rings. 



From the fact that, in the oocyte, the splitting of the diplotene 

 filaments appears to correspond with the plane in which conjugation 

 takes place, it is inferred that segregation of homologous chromosomes 

 is effected in the heterotype mitosis. The elimination of " chromatin " 

 particles in the diffuse stage of the oocyte nucleus has been fully investi- 

 gated ; it has been shown that the formation of yolk is consequent upon 

 the elimination of material from the plasmosome, and the suggestion is 

 made that similar nuclear particles in other animals arise from the 

 plasmosome. J. A. T. 



Respiration in Dragon-fly Larvae. — Hans Wallengren {Lunds 



o 



Univ. Arsshft., 1915, 11, No. 11, ;'>-12). In Vv'ater with normal 

 oxygenation the oxygen content of the tracheal air is always lower, and 

 the C^02 content the same as or a little higher than that of the water 

 used in the respiration. The diflference can be explained according to 

 the laws of diffusion. The tracheal air varies with the oxygenation of 

 the water, but has always less oxygen. From the tracheal gills the 

 oxygen diffuses into the large dorsal and ventral tracheas. By the 

 breathing movements, the body movements, the contractions of the 

 walls of the respiratory part of the intestine, as also by diffusion, 

 the oxygen passes into the finer branches and is absorbed by the l)lood, 

 the tissue-bathiug fluid, and the cells themselves. The carl )on- dioxide 

 given off by the cells is dissolved in the tissue-bathing fluid and the 

 blood, and only a small part passes into the tracheal system ; the rest 

 diffuses from the blood through the skin, the tracheal gills, and the wall 

 of the respiratory part of the intestine directly into the gut. When the 

 insect gets into respiratory difficulties, the oxygen percentage in the 

 tracheal air sinking below 4 p.c, cei'tain reflexes are put in operation 

 and the larva comes to the surface. When they increase the percentage 

 of oxygen in the tracheal air to about 12 p.c. (high above the normal 

 in sub-aquatic life) the larvBS return from the surface. J. A. T. 



Maturation of Parthenogenetic Ova of Aphis palmse. — V. I), de 

 Baehr {La Cellule, 11)2(», 30, 317-49, 1 pi.). In the oogonia there 

 are always eight chromosomes. These are reduced in the synaptic 

 prophase to four bivalent or diakinetic chromosomes. In the matura- 

 tion these are analysed into their components, and, since no maturation- 

 spindle is formed, these remain in the nucleus. Eight simple chrono- 

 somes are seen, as in the oogonia. This may be compared to the first 

 maturation-division in the male germ-cells or in the winter ova. But 

 in the parthenogenetic ova there is no mechanism for transporting the 

 dissociated chromosomes in opposite directions. The single maturation 

 mitosis which is realized in these ova corresponds to the ordinary 

 second maturation -division and not to the first. J. A. T. 



Aphids of the Rose and other Plants. — Edith M. Patch {Bull. 

 Maine Aijric. Station, 1919, 282, 205-48). For many years after 

 Linnteus gave " the " rose aphid the specific name of rosse, this term 



