N. Y A TS ti. 



(35 



arm-apparatus is best observed in younger individuals. 



Among tbe specimens front Hyakkanzeki I found some shells, 

 both valves of which are partially covered by some tubes of polychaetous 

 Annelids, lying parallel to the longitudinal axis of the shell. 



The peduncle has a great regenerative power. We often meet with 

 large individuals with a very small and slender peduncle. As for the 

 mode of regeneration T shall put it off till I study this structure more 

 carefully. 



As for the spawning habits of Lingula the reader is referred to my 

 embryological paper.* 



It is not an easy task to determine how long the life of Lingula is. 

 To do this one must observe definite specimens in aquaria as well as in 

 their natural habitat for many years. Morsk (73) states " they 

 [Giuiuaia. were all of the same size and their life does not exceed 

 one year" (p. 46). Somewhat later François ('91) has declared 

 that Lingula lives " au moins plus d'une année " (p. 232). The 

 small individuals I was able to secure in the autumn at Misaki were 

 5 mm. in shell length on an average. Assuming that the growth of the 

 shell goes on constantly and also that there is only one spawning season 

 in the year, the fact that smaller individuals than the above size do not 

 occur, proves that it takes oik; year for the larvae to grow up to this 

 size. To attain the maximum length (35 mm.) of the shell at Misaki 

 at the same rate would require 7 years. Accordingly, the conclusion 

 is not unreasonable, 1 believe, that at Misaki Lingula lives for five 

 years or more on an average. 



That Lingula could have lived and survived throughout the whole 

 geological periods is due, one would naturally suppose, to their great 

 power of withstanding unfavorable conditions. This is proved by the 

 fact that Lingula lives for a considerable lengthe of time in aquaria 

 even after the water has become spoiled and foetid. A remarkable 

 case justifying the above supposition has been brought to my notice 



* X. Yatsu "On t)i.' development of Ungula anatina Bboo." .lour. Coll. Sç. Vol, 

 XVII (in press.). 



