584 REPORT— 1898. 



abundantly at Cumbrae, N.B., but unfortunately antheridic specimens are 

 not common, so, having ascertained that it grows at Plymouth, I thought 

 it advisable to try that locality at Easter. At Plymouth I was not able 

 to secure it in quantity, but through the kindness of the Director of the 

 M.B.A. Laboratory I was able to secure a fair number of plants by 

 dredging at different times off Mount Edgecumbe. It is a distinctly 

 interesting fact that they were practically all antheridic. Mr. A. H. 

 Church, in his interesting paper on Cutleria (The Polymorphy of Cuthria 

 multifida, Grev., 'Annals of Botany,' vol. vii. No. 45, March 1898), 

 points out that that plant seems to have what I think might be called 

 isotherms of fertilisation ; that is to say, the temperature of the sea seems 

 to largely determine the presence of sexual organs and also their power to 

 unite sexually. If he is right, there is an optimum below which fertilisa- 

 tion cannot take place, but undoubted parthenogenesis of the oospheres. 



If Mr. Church's views are correct — and they seem well supported by 

 the evidence — then the negative results with regard to Tilopteris may be 

 accounted for. 



My own results did not differ essentially from those of previous 

 observers. The plants were repeatedly under observation, especially early 

 in the morning, and were frequently seen to discharge both spermatozoids 

 and oospheres ; but there was no sign of the latter exercising an attractive 

 influence on the former, as is so easily seen to be the case with such 

 oogamous Phseophycese as Fucue. Further, the presumptive oospheres 

 were in certain cases extruded under conditions which rendered access of 

 spermatozoids impossible, and yet they germinated freely, giving rise to 

 characteristic young plants of T. Mertensii in the course of a month. ^ The 

 conditions of temperature were varied as much as possible, but no other 

 result was obtained, the oospheres under no conditions exercising an 

 attractive influence on the spermatozoids. It is very difficult to keep 

 these rather delicate sea-weeds under continuous microscopic observation 

 in anything like natural conditions ; but with improved methods of treat- 

 ment it is possible positive results may yet be obtained, and it is my 

 intention to renew my attempts at the proper season in the hope that a 

 definite positive result may be reached, for I am inclined to believe in the 

 sexuality of the organs under investigation. 



In conclusion I have to tender my best thanks to the Appointing^ 

 Committee for the privilege of using the British Association Table during 

 the period named. 



Report on Nerves of Arenicola, Nereis, &c. By F. W. Gamble, M.Sc. 



While recently investigating the anatomy of several species of Arenicola 

 I discovered in A. Gruhii certain nerve-cells which, from their size 

 (averaging 65/a in diameter) and their definitely segmental arrangement, 

 differed very markedly from other elements of the cord. Accordingly, 

 when nominated to occupy the Plymouth Table by the British Association^ 

 Committee, I determined to apply some recent methods to fresh material, 

 and for this purpose selected the methylene-blue method. 



In addition to species of Arenicola the following genera were tried .- 

 Polynoe, Lepidonotus, Sigalion, Sthenelais, Aphrodite, Halosydna, Nereis, 

 Nephthys, Glycera, Capiitella, Terebella, Chcetopterus, and one of twO' 

 undetermined Sabellids. Ophryotrocha and larvjB of Terebella and of 

 Folyophthalmus were also experimented with. 



The method was that of Ehrlich as modified by Allen ('Q.J.M.S.,' 



