726 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Molluscoida. 



" Olfactory Tubercle " of Simple Ascidians.* — In this paper 

 Dr. W. A. Herdmann investigates the value of this organ " as a 

 specific character " ; but he points out that in retaining the name he 

 recognizes the importance of Julin's recent investigations as throwing 

 " grave doubts on the supposed sensory function of this organ." He 

 describes its position on the branchial sac and its relations to neigh- 

 bouring parts ; to the wedge-shaped space between the two peri- 

 pharyngeal bands which bound the zona jprcebrancliialis he gives the 

 name of " peri-tubercular area." He says that when a little compli- 

 cated, " the curves into which the band of the tubercles may be twisted 

 and the resulting shapes of the organ seem infinite." There is no 

 doubt that the characters vary according to the family, genus, and 

 species ; but Dr. Herdmann finds that it is subject also to great indi- 

 vidual variations in some species. To test this matter further, eight 

 common species were carefully examined, and the range of variation, 

 which again differs in different species, was studied by the aid of a 

 large series of specimens. 



Organization of the Simple Ascidians-f — In his previous contri- 

 bution, J M. Charles Julin refrained from giving an opinion as to the 

 functions of the hypophysis ; further studies lead him to think that 

 the question can now be well answered in the terms of Professor van 

 Beneden's report to the Belgian Academy of Sciences : " It is pro- 

 bable that the products of the hypophysis of Phallusla mammillata are 

 excretory products. Physiologically, then, the organ would be a 

 kidney. If this is the case with P. mammillata, it is very probable that 

 it is the same also in the case of other Tunicates." When we examine 

 the structure of the gland, we find that, unlike most glands, there 

 is more than one excretory orifice ; 128 ciliated infundibula were 

 found completely developed in one not adult individual. These funnels 

 have been found to be formed at the expense of the blind ends of the 

 canals, and to come into connection with the exterior by the absorp- 

 tion of the peribranchial epithelium. 



The hypophysial apparatus of the adult Phalhisia is described as 

 having the following structure. It is 31 mm. long and has a prin- 

 cipal canal, the calibre of which varies considerably at different 

 points. The principal infundibulum is strongly pigmented and 

 opens by a circular orifice into the buccal cavity ; the glandular 

 mass itself is only If mm. long. There are secondary canals and 

 infundibula ; the glandular mass is seen to diminish, while the 

 system of secondary canals increases as the animal grows older. 

 The principal canal gives off a number of secondary branches, 

 which again ramify ; these ramifications unite, and give rise to a 

 plexus on the dorsal face of the animal ; the calibre of the different 

 canals varies considerably, but they all have their walls formed 

 of a cubical epithelium. As compared with the earlier stages, the 



* Proc. K. Phys. Soc. Ediii. (1881) 14 pp. 

 t Arch, d.i Biol., ii. (1881) pp. 211-32 (1 pi.). 

 X See this Journal, ante, p. 590. 



