246 



of a large number of animals in the tropics would still be very useful." 

 (Op. cit, p. 355). 



With the latter sentence I most heartily agree, but otherwise I musl 

 decidedly object to the statement that in the tropical seas the animals are 

 continuously breeding - at least as regards the Echinoderms, and I can- 

 not but wonder how Semper came to the above result. It is true that I 

 have made only few observations, as regards this point, during my stay at 

 the Philippines; but at any rate I found that the large Synapta Beselii had 

 no ripe sexual products in February March at Zamboanga. And it is 

 certainly not to be assumed that the animals behave otherwise at the 

 Philippines than elsewhere in the tropics, as regards their breeding. My 

 observations decidedly prove that at least several of the littoral Echino- 

 derms do not breed continuously. Thus e. g. I never found the opportunity 

 for studying the development of Diadema, until I came to Tobago, B. W. I. 

 and there found D. anlillamm to have ripe sexual products in the end of 

 March; and when, about a week later on, I wanted to start a new larval 

 culture it was impossible to find one specimen containing ripe sexual pro- 

 ducts, all were quite empty. A similar experience I had with Echinometra 

 nan Brunli, Brissus obesus, Slichopus Kefersteinii, and in several cases I 

 had, to my great annoyance, to give up any hope of obtaining a larval 

 culture, because the breeding season did not coincide with my stay (e. g. 

 Echinonens). - On the other hand, I have some observations tending 

 to show that in the tropical seas Echinoderms (some forms, at least) have 

 more than one breeding season in the year. But for proving this defini- 

 tely observations must be continued through a longer period, a stay of a 

 few months being, of course, insufficient for such a task. 



I would recall here that I have been able to prove (Die Echinoiden d. 

 Deutschen Siidpolar-Expedition, p. 71) 1 ) that the Antarctic Sterechinus 

 Neumayeri breeds at least from June to April, which fact is doubtless due 

 to the very uniform temperature reigning in the Antarctic Sea throughout 

 the year. This case then confirms Orton's statement that "where bio- 

 logical conditions do not vary much, marine animals will breed continu- 

 ously." I would only object to making this a general rule; this it is cer- 

 tainly not, especially not in the tropics. 



') Deutsche Siulpolar-Expedition. Zoologie. III. 1909. 



