On the Life-History and Development of the Genus Myzostoma. 567 



Notes on the Biology of the Oenus. 



If Comatulae be taken from various parts of the bay of Naples tlie 

 number of both species of Myzostoma found on them will be foimd to 

 Vary with tlie place of capture. In tbe impure water near the shore the 

 Comatulae are infested with very few Myzostomidae, while the opposite 

 extreme is reached in those caught in the elear pure water near the 

 island of Nisita, where most of the Comatulae are infested with M. 

 cirriferum and many of them also with M. glahrum. Indeed M. gla- 

 hrum is pretty abundant in this spot, and large specimens are found. 

 The numbers of the two species found on a given Comatula vary very 

 much, but the statistics given under this head by Prof. Graff i — so far 

 as they concern M. cirriferum — are not correct. M. glabrum is much 

 more rare than M. cirriferum^ and probably the relative frequency of 

 its occurrence given by Graff is correct — that is that about every 

 third Comatula is host to a M. glahrum. If a living Comatula be placed 

 in alcohol a great number of M. cirriferum will fall of it , especially if 

 the animai be shaken in it. Probably the usuai number oiMyzostoma 

 cirriferum on one Comatula is on the average at least double the num- 

 ber ten given by Prof. Graff. In some cases great numbers may be 

 found on one Comatula. In one example I counted on a disc and a 

 small portion of the arms of a Comatula killed in sublimate not fewer 

 than 23 large M. cirriferum. The remainder of the arms had been out 

 away, and probably those portions had many M. cirriferum on them. 



The number of large M. glahrum crowded around and partly 

 within the mouth of a Comatula is often such, that it is hardly possible 

 that the host can get much to eat for itself. The food of Myzostoma 

 is naturally limited to some portion of that of Comatula. It chiefly 

 consists oflnfusorians, Algae, Diatomaceae and other minute organisms. 

 In fig. 35 is figured part of a transverse section of a male of M. gla- 

 hrum , which has devoured and partly digested some of the eggs of the 

 hermaphrodite on which it sat. 



The time of reproduction does not appear to me to be confined to 

 any particular season of the year. Although I have not investigated 

 living Myzostomidae in summer and autumn it appears to me that 

 Graff's view that summer is the chief period of reproduction, at any 

 rate in Naples , is not correct. Myzostoma like many other parasites 

 seems to be compelled to be continually in a state of sexual maturity 



1 1. c. p. 76. 



