203 



PRELIMINARY NOTE ON THE REMARKABLE, 

 SHORTENED DEVELOPMENT OF AN AUSTRA- 

 LIAN SEA-URCHIN, TOXOCIDARIS ERYTHRO- 

 GRAMMUS. 



By Dr. Th. Mortensen, Copenhagen. 



(Gomviunicated hy Dr. S. J. Johnston.) 



During a visit to Australia in August-October, 1914, I was 

 very anxiously looking for opportunities for studying the de- 

 velopment of Australian Echinoderms in continuation of the 

 researches carried out in Japan, in April- July of the same year. 

 It proved, however, to be a very unfavourable time of the year 

 for that purpose, not a single species of Echinoderms having ripe 

 sexual products — except the small Asterina exigiia, which, as has 

 been made known by Whitelegge, has care of its brood, like the 

 European species, Asteri7ia gihhosa. I had then to alter my 

 plans to some extent, and went to New Zealand in the beginning 

 of November, one month earlier than originally planned. In 

 that way, I could arrange for a stay in Sydney during the later 

 part of the summer, February-March, at which time it might be 

 expected that the majority, at least, of the littoral Echinoderms 

 of Port Jackson would prove to have ripe sexual products. 



To my surprise, even this turned out to be a little too early 

 in the season for my object. Of the Echinoderms, of which 

 material in any sufficient quantity was available, only one species 

 — always Asterina exigua excepted — was really in the breeding 

 season now, namely, To.vocidaris erythrogrammus . Of the three 

 other common littoral sea-urchins, one, Centrostephanns Rodgersii, 

 was still very far from having l-ipe sexual products; it must, 

 evidently, have its breeding season in the middle of the winter; 

 the two others, Phyllacanthus parvispinus and Holop)neustes pur- 

 purascens, were nearly ripe, but not quite. Among the other 

 Echinoderms, of which material was available, not one was found 



