606 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The author promises to give further details, and to demonstrate 

 how the openings are connected with the Mood-passages. He regards 

 the water that is taken as having a respiratory as well as an erectile 

 function. 



Sexuality of the Oyster.* — M. Bouchon-Brandely points out that, 

 while the common oyster [Ostrcea edulis) is hermaphrodite, the Portu- 

 guese form (0. angulata) is unisexual. In the latter the ova are 

 expelled from the shell and fertilized in the water. The characters of 

 their development are such as to yield no support to the doctrine of 

 hybridization taught by some French ostreiculturists, and artificial 

 fertilization of the two species has never yet been found to be success- 

 ful. Artificial fecundation of 0. angulata was, however, effected, and 

 it was observed that the shell is formed on the sixth or seventh day 

 after impregnation. The genital gland of this species does not have 

 its elements matured until the time when it becomes transparent. 

 Having been successful in small attempts at artificial fertilization, the 

 author has successfully attempted some experiments on a much larger 

 scale. 



Arthropoda. 

 a. Insecta. 



Respiratory Movements of Insects- f — F. Plateau finds, as the 

 chief results of his experiments, that — 



1. There is no close connection between the character of the 

 respiratory movements of an insect and its systematic position. The 

 respiratory movements are only analogous when there is very nearly 

 the same structure of the abdominal rings, and of the muscles which 

 move them. For example, the respiratory movements of the 

 Phryganida do not resemble those in allied Neuroptera, but are much 

 more similar to those of the aculeate Hymenoptera. 



2. In all insects the diameter of the abdomen diminishes during 

 expiration, owing to the approximation of the tergal and sternal pieces. 

 The former, as in the Coleoptera, may alone be mobile, or the latter, 

 as in AcrididaB, Libellulidse, Lepidoptera, and Muscidse ; or the two 

 may move equally, as in TipulidaB, Sialis, and a few others. 



3. The modifications in the vertical diameter may be accompanied by 

 changes in the transverse diameter, as in the Libellulidse, Chrysopidse, 

 some Coleoptera, &c. 



4. Contrary to what was formerly believed, it has been found that, 

 during normal respiration, changes in the length of the abdomen are 

 rare ; they are to be seen in the aculeate Hymenoptera, and in such 

 isolated cases as the Phryganidsa among the Neuroptera, and the 

 Coccinellidae among the Coleoptera. 



5. In most cases the thoracic segments take no share in the 

 respiratory movements when the animal is at rest, but they have been 

 observed to do so in some genera of Coleoptera. 



6. Contrary to the opinion of most observers, M. Plateau thinks 

 that the respiratory wave is an exceptional phenomenon. It has not 



* Comptes Eendus, xcv. (1882) pp. 256-9. 



t Bull. Acad. R. Sci. Belg., iii. (1882) pp. 727-37. 



