372 SECTIONAL TRANSACTIONS.— D. 



in this way for the needs of the young fish immediately after hatching. During 

 the initial stages of free existence the young fish feeds chiefly on amphipods 

 and small crangonids. Post-embryonic changes are well defined. The tip of 

 the tail, behind the second dorsal fin, is gradually absorbed and becomes quite 

 short in comparison with the embryonic elongation. 



Specimens and photographs were exhibited of nine species, eight of which 

 were secured at Plymouth and reared in the laboratory tanks. These included 

 a complete developmental series of embryos, egg capsules, newly hatched young, 

 and voung fish up to a few months old. 



Monday, September 11. 



13. Joint Discussion with Section K en The Present Position of 



Dancimsin. (See p. 399.) 



14. Mr. A. M. Caeb-Saundees. — Problems of GeograjMcal 



DisirihuHon in Spitsbergen. 



15. Prof. A. Meek. — The Fate of the Segmentation Cavity of the 



Frog's Egg. 



16. Prof. E. B. PouLTON, F.B..S.— Experimental Evidence for the 



Hereditary Transmission of Small Variations sucli as woidd, 

 be required to initiate a Mimetic Resemblance in Butterflies . 



The sudden evolution of a complex mimetic pattern, fully formed and 

 complete, is difficijlt or even impossible to explain. We are compelled to 

 believe that there has been a development in stages, each represented by a 

 comparatively small variation. Certain authorities on heredity have main- 

 tained that such variations are not transmitted. An investigation designed to 

 test this conclusion has been carried on with the common Currant Moth 

 {Abraxas grossuhiriata), and it has been shown that the fusion of two black 

 patches on the fore wing into a single bar, present in the female parent, was 

 transmitted to nearly all of her offspring. Next year will probably decide 

 whether the transmission followed Mendelian laws; but, Mendelian or non- 

 Mendelian, the variation was certainly hereditary, and was of just such a kind 

 and magnitude as would furnish one of the steps towards a complex mimetic 

 pattern. 



17. Mr. C. Tate Regan, P.R.S. — Some Examples of Adaptative 



Evolution in Fishes. 



Three examples were given illustrating a marked adaptative evolution without j 

 any other change of structure. (1) Ccecobarhufi, from a small subterranean lakej 

 in the Lower Congo, may be described as a Barbus that has lost its eyes and 

 its pigment and has developed the lateral line system. (2) Epibulus insidiata, 

 of the Indo-Pacific, may be described as a C'heilinus with an extremely pro- 

 tractile mouth ; the quadrate bone is long and freely movable. (3) Echencis 

 is a Percoid with the spinous dorsal fin represented by a suctorial disc on the 

 head, the fin spines being transverse laminre. It may have originated from a 

 pelagic fish with habits like the pilot fish {Naurratcs). 



18. -A. meeting took place at the Town Plall in Grimsby at 7.30 p.m., 

 when Dr. E. J. Allen, F.R.S., and Prof. J. Stanley 

 Gaedinee, P.E.S., opened a discussion on Scientific Fishery 

 Research and the Fishing Industry. 



