THE ZOOLOGICAL STATION AT NAPLES. 387 



Among other observations upon Codenterata, I have observed the 

 existence of a continuous longitudinal strip of cells with granular proto- 

 plasm situated in the ectoderm and extending along one side ol the 

 tentacles of certain Hydrozoa. I have demonstrated the existence of this 

 band of cells in the tentacles of the medusaj of Carmarina and in those 

 of the hydropolyps of Obelia, Uiidendrinm, and Aglaophenia, and I have 

 no doubt that it can be demonstrated in other genera also. This band 

 of specialised cells can be made obvious by keeping the living animals for 

 some time in sea-water tinted by methylene blue in the proportion recom- 

 mended by Zoja.' It was found that certain cells along one side of the 

 tentacles became stained, thus demonstrating the existence of the above- 

 mentioned band of differentiated histological elements. 



I was enabled to make very considerable progress with my work on 

 the anatomy of Phyllirhoe, and to make several observations on the living 

 animal, which I hope to publish before the close of the present year. 



Report on the Occupation of a Table at the Stacione Zoologica, Naples, 

 during Marclb and April 1£00. 



e. The Fertilisation Proc^'ss in Echinoidea, 

 By A. II. Reginald Buller, Ph.D. 



I occupied the table of the British Association from March 15 until 

 April 21. 



The research work undertaken was an endeavour to determine whether 

 the eggs of the Echinoidea excrete a fluid which attracts the spermatozoa 

 chemotactically. Bergh ^ states that attraction by a special substance is 

 probable. According to Strasburger ^ the eggs of the Fucacece (which are 

 also fertilised after being set free in sea- water) excrete a substance which 

 attracts the spermatozoa from a distance equal to about two diameters of 

 an egg. 



The material consisted of the following animals : — Arhacia pustulosa 

 Gray, Echinus microtuberculatus Blv., and Sphxerecltinus granularis Ag. 



No attraction could be observed during artificial fertilisation experi- 

 ments. Collections of spermatozoa, however, take place in the outer 

 gelatinous coat of the eggs. Observations were made tending to show 

 that this is a physical and not a chemotactic phenomenon. 



Experiments were then made in which it was sought to collect in sea- 

 water the supposed fluid excreted from the eggs. The eggs were left very 

 thickly placed together for 2-12 hours in a very shallow layer of sea- water, 

 and the latter, after filtration, introduced by means of an air-pump into 

 capillary glass tubes. These were then placed in a drop containing motile 

 spermatozoa. No gathering of the spermatozoa into the tubes could be 

 observed. One precaution taken was to prove that just before filtration 

 the eggs could be fertilised. 



In the case of Arbacia it was discovered that when spermatozoa are 

 introduced into a drop containing freshly extruded eggs they collect into 

 small balls, often composed of 100 or more individuals. The balls were 

 also formed after the water had received four successive filtrations. A 

 tactile stimulus appears to play a part in tlie phenomenon. 



' In his experiments on Hydra, Bend. Inst. Lomh. xxv. 

 ^ Vorlesmngen uher alhienicinp Ewbri/nloffic, 1895, p. 43. 

 ■ I)m botanische Practicuiii, 2te Anil. 1887, p. 402. 



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