MUSEUM OF COMPARATIVE ZOOLOGY. 219 



vessel which connects this radial system of tubes with the cavity of the axis of 

 the colony. The bell margin has a marked velum and is destitute of tentacles. 

 The sperm is found in the inflated proboscis, which fills almost the whole bell- 

 cavity. This receptacle is in older male bells, and in those especially which 

 are found near the extremity of the polyp-stem, of a milk-white color. The 

 spermatozoa have a rounded head and small vibratile tail. The clusters of 

 female bells which occur with the male have a similar attachment, and are also 

 campanulate, resembling those of Agalma. Each bell carries a single ovum. 

 Individual eggs and bells voluntarily separate from the attachment to the 

 colony, and the latter live for some time free in the water. The ova of Nano- 

 mia can easily be seen by the unaided eye, as they float about in the water in 

 which a parent Nanomia is captive. 



A method of collecting the ova is to allow the Nanomia to remain quiet for 

 some time m a glass jar. This jar contained about three gallons of water, and 

 was so placed on a table that one could see through its sides, the window 

 or source of light being on the opposite side of the jar. In this way the 

 ova could readily be distinguished in the water, and after a few hours they 

 rise to the surface. When they are seen floating at diff'erent depths in the 

 water, it is possible to pick them out one by one with a pipette. When the 

 ova rise to the surface it is more convenient to skim them off by means of 

 a watch-crystal, or some similar shallow receptacle. ( 



Development. — The development of the older larvae of Nanomia, after the) 

 formation of the float, has been well described by A. Agassiz in his account 

 of the animal, to which reference has already been made. He considers that 

 there are two methods of development, one from the egg, and the other by 

 budding from the parent colony His figures are mostly from stages which he 

 regards as formed by the latter method, and are of larvae after the float has 

 already formed. 



It is certainly an exceptional method of growth of new colonies of Siphono- 

 phores to find the young budding from the parent, and new observations - are 

 desirable to determine the details of such growth. There is no known genus i 

 which resembles Nanomia in this respect, and all other 'genera, whose embry- 

 ology is at present known, reproduce new colonies by ovulation alone. The 

 following observations have a bearing on the origin of the larva of Nanomia, 

 although they leave the important question in doubt. 



A minute comparison of the float of the parent colony with the " oil glob- 

 ule " of one of the tasters was made, in order to detect differences and resem- 

 blances, if any, between them. While it was found that there are marked 

 differences in these two structures, I could not say ^hat the differences would 

 prevent the one being a development of the other. Still, I have not been able 

 to persuade myself that such is the case. I have repeatedly found the tasters 

 with their oil globules detached from the parent axis, but all attempts to raise 

 these into older stages similar to those figured by A. Agassiz have failed. 

 There is one point in which there is a great difference in the tasters which I 



