400 On Alternate Generation of Annelids, 



young embryos, bursts, and then the females disappear. 

 It is probable that they are killed by this, as I have never 

 succeeded in finding a single female after it had discharged 

 its embryos. The agaraous individuals continue to live 

 after the separation of the males and females. New rings 

 are formed, (PI. XL, fig. 7) ; and the same process appar- 

 ently begins again, (PL XL, fig. 6,) as I have frequently 

 found parent stocks from which sexual individuals had evi- 

 dently already been separated, in the state represented in 

 this figure. I am unable to say how many times this is 

 repeated, and what is the length of life of the parent 

 stock. They are found in large numbers on the stems of 

 all the Campanularians of our bay, where they build 

 their thin, transparent cases. Especially numerous upon 

 those Campanularians which are attached to Laminaria. 

 This same species I have also observed south of Cape 

 Cod, in Buzzard's Bay. 



I did not observe the young embryos while they were 

 still inclosed in the bag of the female; my principal object 

 being to satisfy myself about the alternate generation, and 

 to see how far the mode of development by division from 

 the parent stock agreed with the more advanced stages of 

 the embryo after it had left the egg. The young, when it 

 escapes from the bag in which the eggs come to maturity, 

 is triangular, tapering very rapidly towards the posterior 

 extremity (PI. X., fig. 2) ; it has two large eyes quite dis- 

 tinctly marked. The alimentary canal (F) follows the 

 outline of the young embryo ; it has slightly undulating 

 walls corresponding to two very faint constrictions, one 

 directly behind the eyes, and the other at the same dis- 

 tance from the posterior end. There is no appearance of 

 a mouth. In the next stage (PI. X., fig. 3) the indenta- 

 tion behind the eyes becomes more deep, thus separating 

 slightly the head from the rest of the body, the anterior 

 part at the same time bulging out, (PI. X., fig. 3, A), the 



