THE ZOOLOGICAL STATION AT NAPLES. 693 



cross, however, only about 1 per cent, of the ova reached the pluteus 

 stage, and these plutei were 13-2 per cent, smaller than the pure maternal 

 larvne. 



Crosses were also effected between the forms mentioned and Arhacia 

 pusiulosa, Echinocardium cordatum, Echinocardium mediterraneum, 

 Doroeidaris painllata, and Echinus acutus. Also the various colour 

 varieties of Sphcerechinus were crossed, a distinct diminution of fertility 

 being found to exist between dissimilar varieties. With the colour 

 varieties of Strongylocentrotus, however, this was not the case. 



In conclusion, I wish to offer my thanks to the Committee of the 

 British Association for the privilege of being allowed to hold the table, 

 as well as to the authorities at the Zoological Station at Naples for their 

 invariable kindness and for the facilities they were able to afford me in 

 my work. How great these were may be gathered from the fact that I 

 was able to carry on the chemical, physiological, and bacteriological por- 

 tions of my work simultaneously. As regards echinoid material also I 

 was afforded an absolutely unlimited amount, and as regards the artificial 

 fertilisations I was enabled, when necessary, to keep fifty or more large 

 jars of plutei developing at one and the same time. 



III. — On the Variation of Cardium, Donax, and Tellina. 

 By J. Parkinson. 



It was my intention in visiting the Zoological Station at Naples 

 during the winter of 1897-98 — i.e. from November to April inclusive — 

 to attempt an investigation on the reproduction of certain Ascidians. 

 However, a short visit to Plymouth, with some subsequent study, early in 

 last year raised sundry objections, and on reaching Naples in the begin- 

 ning of November I gave up the subject which has just been mentioned, 

 taking in its place the one which appears at the head of this report. I 

 began upon the genus Area, comparing the variation in certain propor- 

 tions exhibited by the commoner species of that genus one with another, 

 but found after several attempts that the confined space in which the 

 animals grew, due to the nature of their attachment, raised great diffi- 

 culties in the way of forming any true estimate of their natural variation. 

 I then proceeded to the genus Cardium, and subsequently to the genera 

 Donax and Tellina, comparing the variation in the chosen proportions of 

 the several species one with another, as in the case of Area. Here I was 

 more successful ; but in finding a reasonably certain, and, at the same 

 time, fairly quick method of measuring, as well as in overcoming the 

 difl[iculty of obtaining definite points from which to measure, much time 

 was spent. The work is now undergoing entire revision in the laboratory 

 at University College, London. Material for subsequent investigation 

 was also obtained from such experiments as the resistance of Pecten to 

 diluted sea-water, but this has not yet been studied. Although a con- 

 siderable number of measurements have been made, I have not at 

 present reached that degree of certainty which makes it desirable that 

 results should be given in length. It gives me great pleasure to testify 

 to the extreme kindness shown by all the members of the station at 

 Naples, especially to Signor Lo Bianco for the efibrts he made to satisfy 

 my rather large demands for material. To Professor Weldon my warmest 

 thanks are gratefully given for the very kind help he has afforded me 

 not only by letter, but since I returned to England. In doing such work 

 as that indicated above this has been simply invaluable. 



1898. Q Q 



