496 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The conchiolin tube commences as a closed sac fitting into the 

 sheath of the apical chamber ; it extends unchanged in thickness through 

 the first funnel ; from the second to the fourth septum the tubes are 

 much attenuated. At about the fifth, the tubes no longer pass through 

 the funnels, but become disconnected. The older funnels are made up 

 of five layers : — (1) an outer layer formed by the anterior end of a 

 posterior sheath, where it embraces the funnel ; (2) a darker and denser 

 layer than the oiTter layer which contains more organic matter ; (S) the 

 shell layer of the funnel proper ; (4) the dense layer forming the 

 anterior end of an anterior spicular sheath ; and (5) an inner layer that 

 is extremely short, and reduces the opening of the funnel at its posterior 

 end. The last two layers are not present in the funnel of the living 

 chamber. 



So-called Organ of Verrill in Cephalopoda.* — Dr. J. Brock points 

 out that the so-called organ of Verrill in Cephalopods was discovered 

 and described by Heinrich Miiller more than thirty years ago, while 

 Bobretzky has made some observations on its development. The recent 

 statement of Mr. Laurie that the organ is absent from the adult Loligo 

 and OmmastrepTies is probably due to the fact that preserved material 

 only was examined ; Miiller himself was aware that the funnel-organ 

 was completely destroyed by the ordinary preservative fluids. The 

 organ, indeed, has been seen in so many Cephalopods that it may well 

 be said to be found in the class as such. The author confirms the 

 account given by Miiller as against the discrepant description of 

 Laurie.f 



j8. Pteropoda. 



Morphology of Spinous Sacs of Gymnosomatous Pteropoda. | — Dr. 



P. Pelseneer objects to the view recently enunciated by P. Schalfejefif 

 as to the homology of the " sacs a crochets" with any part of the arms 

 of Cephalopoda. These arms and the organs which they carry are 

 entirely pedal in nature, while the sacs of all the Gymnosomata are 

 inserted on the internal wall of the buccal cavity. As the Aplysina 

 have the greatest affinities to the Gymnosomata they should be examined 

 when it is sought to explain the nature of the sacs ; now, in Notarclms 

 the buccal cavity is lined by spinous hooks, and those found in the 

 Pteropods are only specializations of the spinous palatine vault of 

 Notarclms. It is to be noted that the sacs are not always as long as in 

 Clione or Pneumodermon ; in Dexiobranclisea, which is the most primitive 

 of existing Gymnosomata, and in Clionopsis they only form slight 

 depressions in which the hooks are implanted. 



y, Grastropoda. 



Ventral Nervous Mass of Fissurella.§ — Dr. L. Boutan deals with 

 some criticisms of Dr. B. Haller. That author has asserted that the 

 ventral nervous mass forms a homogeneous centre in which two distinct 

 portions cannot be made out ; and that the centre is single. Dr. Boutan 

 declares that this is not the case, for two centres may be fused histolo- 

 gically, and yet be distinct morphologically, and this is the case with 

 Fissurella and a number of other Molluscs. 



* Naclirich. K. Gesell. G6ttino;en, 1888, pp. 476-8. 



t See this Journal, 1888, p. 932. J Zool. Anzeip-., xii. (1889) pp. 312-4. 



§ Arch. Zool. Expe'r. et Gen., vi. (1888) pp. 375-421 (3 pis.). 



