CONTKIBUTION TO AN EVALUATION OF THE SEA. 325 



The life-history of C. intestinalis is very similar to that of the 

 Sycons described above. It has been definitely established that the 

 species dies down about October, at about which time very fine 

 specimens upwards to a foot long can be obtained. This fact has, 

 however, been known at this laboratory for several years. By the 

 end of October it is difficult to find Ciona of even medium size, but 

 very small specimens are not uncommon. Breeding commences again 

 after the winter season about April, and from April to October specimens 

 may attain to a length of 15 cms., while those which have wintered and 

 are practically a year old at this time have been found to attain a length 

 of 30 cms. It is thus evident that Ciona is an annual, but passes through 

 at least two generations in a year, and in favourable seasons may yield 

 three, rushing through two generations in the autumn, as in the case of 

 the Sycons. Thus these observations support the statement made by 

 Anton Dohrn that Ciona at Naples passes through three generations in 

 a year. (See footnote, p. 326.) The life-history of C. lepadiformis has been 

 found to be very similar to that of C. intestinalis. It appears in this dis- 

 trict about the end of April — apparently growing from dormant stolons 

 — and grows to huge colonies during the summer, and at the same time 

 passes through at least two generations. At about October these colonies 

 die down and nothing is to be seen of them during the winter until about 

 the following i\.pri]. 



A. asyersa has a somewhat similar life-history, but does not 

 die down as completely in the autumn as Ciona. Between April and 

 September this species has been found to grow to a length of 9 cms., 

 very nearly the maximum size. M. ampulloides ? has also a very 

 similar life-history to that of Ascidiella, and gives quite good fertiliza- 

 tions at an age of 3 months, and this sub-spherical Ascidian may 

 attain at this age a diameter of 2-5 cms., a size not far from the maximum 

 for this species.* 



KATE OF GROWTH IN SOME OTHER TUNICATES. 



Botryllus violaceus gives off larvae at an age not greater than 3 months 

 and grows to large colonies during the summer. Thus in the case of all 

 these Ascidians there are at least two crops of larvae produced in a year, 

 and in some of them, as in Leptoclinum, Clavellina, and Botryllus, there 

 may be three or more crops in favourable seasons. 



* Development in this species is remarkably rapid ; the fertihzed egg developing into 

 a metamorjohosing larva in less than 24 hours. 



