24 Prof. Mtiller on the Development 



my infinite astonishment, while in one individual I found in the 

 anomalous genital organ, sacs containing ova undergoing the 

 process of yelk-division, in another the same organ contained 

 similar vesicles in which young mollusks with spiral shells T \yth 

 of a line in diameter were included. 



This was the commencement of the researches which I con- 

 tinued uninterruptedly for two months, and in the course of 

 which I observed sixty-nine times the occurrence of mollusks or 

 mollusk-yelks in this Holothuria. 



The individuals which contain mollusks agree in all respects 

 with the normal individuals of Synapta digitata ; they possess the 

 same twelve four-fingered tentacles, the same structure of the 

 integument, the same calcareous plates and " anchors " to which 

 their adhesive power is due. Another kind of Synapta, the 

 S. inhcsrens, occurs also, but more rarely, in the Bay of Muggia ; 

 it is however certain, that all I have to say concerning the pro- 

 duction of mollusks in Holothuria relates to S. digitata. 



The Synaptce were taken at a depth of from 6-8 fathoms in 

 fine mud not far from Muggia, and were regularly brought to me 

 every day from Zaole*. These Synapta, like all their congeners, 

 have the habit of breaking up spontaneously when roughly 

 handled, and were not to be obtained in an entire state ; 

 the daily supply therefore consisted of fragments of Synapta 

 which had a maximum length of 8 to 10 or 12 inches. Among 

 them anterior portions with the head were to be found. 



The head once separated, the fragments, however long they 

 may be, do not break up again, but remain living and moving 

 for a day or more ; a piece with a head, however, redivides as 

 often as it is irritated, and it is only by longitudinally dividing 

 the head that this process can be finally stopped. 



It is, hence, impossible for me to say exactly how long the 

 Sxjnapta digitata is, but I estimate its length at 15 to 20 inches. 

 From the same cause also, it is impossible to determine with any 

 certainty, what is the proportion of individuals with molluski- 

 gerous organs to those with normal ovaria. All that I could do 

 was to put the various fragments of my daily collection together 

 and measure the whole. In this manner a conception may be 

 formed upon how large a mass of materials the labours of these 

 two months were expended. On one day when the quantity of 

 the worms was less than usual, the length of the fragments, 

 placed end to end, was 60 feet ; on another occasion when there 

 were more, it was 79 feet. In so large a mass of fragments 

 one readily found 15 to 20 short pieces with heads, and a still 

 greater number with normal ovaria; at times, though rarely, 



* The fisherman was Mattia Frusing of Zaole. 



