552 SUMMARY OF CURRENT RESEARCPIES RELATING TO 



Lamellibranchs, and the general plan of the vessels would seem to be 

 on the same type. 



The gills are simple in structure and conform to the Lamellibranch 

 type. The generative glands are united in the same individual ; the 

 acini of the testis are large, smooth, or polyhedral, the ovary is also 

 racemose in form, and is placed behind the male organ. After a de- 

 scription of the nervous system and of the muscles, M. de Lacaze- 

 Duthiers sums up the substance of his observations by pointing out 

 that the animal of the watering pot shell is morphologically altogether 

 like that of any other Lamellibranch. After an early period in 

 which development goes on quite regularly, the body, owing to the 

 excessive growth of its lower portion and the stationary condition 

 of the upper, can no longer be withdrawn into its shell ; then there 

 commences a period of abnormal calcareous secretion, which gives rise 

 to the peculiar form of the " shell." But this remarkable phenomenon 

 does not affect the essential characters of the animal, which is much 

 more truly lamellibranch than Tridacna, Anomia, or the oyster. 



In conclusion, the author insists on the value of commencing the 

 study of any given group by the consideration of the anatomy of a 

 normal form. 



MoUuscoida. 



Anatomy of Rhopalsea.* — L. Eoule describes the structure of this 

 simple Ascidian, which is very abundant in the neighbourhood of Mar- 

 seilles. The body is divided into two halves, of which the anterior is 

 triangular and free, while the posterior is irregular in form and fixed ; 

 the two halves are united by a delicate region of some length. The 

 tunic, in its hinder portion, contains a number of vacuolated cells, 

 which are absent from the anterior. By its general facies Bhopalcea 

 resembles the Clavelinidae, but its structure and mode of development 

 associates it with the Phalusiidse ; and it may be considered as forming 

 a link between the simple and compound Ascidians. In some points, 

 such as the postbranchial position of the viscera, it approaches Ciona 

 more than the true PJiallusice, with which, on the other hand, it agrees 

 by the possession of longitudinal folds in the wall of the branchia. 

 Its affinities may be said to be numerous, and to form a bond of union 

 between several diverse groups. 



Arthropoda. 

 a. Insecta. 

 Luciola italica.f — C. Emery, after some observations on the 

 external characters of these insects, and the differences between the 

 males and the females, in which he points out that in the male the 

 whole of the lower of the penultimate (fifth) and last abdominal 

 segments is phosphorescent, while in the female, which has seven 

 abdominal segments, only two spots at the sides of the lower surface 

 are luminous, passes to the structure of the luminous organs, in which 

 there are the following, among other, interesting points. Prepara- 



* Comptes Rendus, xcviii. (1884) pp. 1294-6. 



t Zeitschr. f. Wiss. Zool., xl. (1884) pp 338-55 (1 pi.). 



