414 Di". H. Ludwig on the 



imd Flora des Golfes von Neapel/ and availed myself besides 

 of the favourable opportunity for contributing to the solution 

 of the question which has recently been raised as to the func- 

 tion of the madreporite of Echinoderms in general. The 

 result of the observations which I directed towards this latter 

 point I published some time ago in a paper entitled " Ueber 

 die Function der Madreporenplatte und des Steinkanals der 

 Echinodermen," which appeared in the ' Zoologischer An- 

 zeiger/ no. 339, 1890. Another result of this last visit to 

 Naples is the description which has just appeared * of the 

 rediscovered Risso's Molpadia musculus, and to which I 

 appended observations on the phylogeny and classification of 

 the class Holothurioidea. 



But to return to the principal object of my investigations as 

 stated above, I may begin by remarking that I succeeded in 

 kee[)ing the young of Cucumaria Planci for a much longer 

 time than any one had been able to do before in the case of 

 this or any other Holothurian, as they were kept by myself 

 from March 16 until April 17, and subsequently under the 

 care of the excellent Conservator, Signor Lo Bianco, until 

 July 9, therefore for a period of one hundred and sixteen days 

 in all. On the whole, after the barrel-shaped stage is passed 

 on the eighth and ninth day, the development thenceforward 

 proceeds but very slowly. The larvaj and young animals are 

 so absolutely opaque and so abundantly tilled with calcareous 

 bodies that I was forced to adopt the circumstantial method 

 of careful decalcification and conversion into continuous series 

 of sections, whereby I naturally had recourse to suitable 

 methods of killing and preserving the animals. Owing to 

 the minute size of the cells and the closeness with which the 

 rudiments of the various organs are crowded together, none of 

 the sections had to be tiiicker than 5-7*5 fji, in order to give 

 trustworthy results. In consequence of these circumstances 

 and the large number of iigures required for a minute repre- 

 sentation, the whole study makes considerable demands on 

 time and patience. Publication in detail must therefore be 

 postponed for some time. For the present I would confine 

 myself to communicating as briefly as possible certain results 

 which appear to me to be worthy of notice, while at the same 

 time referring the reader to my critical treatise on the litera- 

 ture of the subject, which has just been published in Bronu's 

 ' Classen und Ordnungen des Thierreiches.' 



As at that time I had no reason for doubting the trust- 



* " Atikp-odcrma musculits (Risso), eine Molpadiide des Mittelmeres, 

 nebst Bemerkungen zur Phylogenie und Systematik der Holothurien," 

 Zeitschr. f. wis,-. Zool. Ed. 51, 1891, pp. 509- 612. 



