PART III THE SUBGENUS CYCLOSALPA. 



I 



BY WILLIAM KEITH BROOKS. 



The subgenus Cydosalpa, including S\ pinnata, S. affinis, S. virgula, and 

 5". floridana, is well marked, and distinguished from other salpas by many 

 structural characteristics. The subgenus owes its name to the shape of the 

 colony of the aggregated form, which is a wheel or rosette, as is shown in 

 figures 8 and 9, plate 2. 



Three of the four known species of Cydosalpa S\ pinnata, S. affinis and 

 S. floridana have in the solitary form, 

 peculiar luminous organs. No luminous 

 organs are described in 5". virgula, and I 

 have had no opportunity to study this 

 species. It is not impossible that these 

 organs will be found to be present in this 

 as in the other cyclosalpas. In S. pinnata 

 the luminous organs are present in the 

 aggregated form as well as in the solitary 

 form. In the other species they seem to be 

 restricted to the solitary form. 



One of the most notable of the common 

 characteristics of the cyclosalpas is the in- 

 testine of the solitary form. This is long 

 and runs upward and forward from the 

 ventral stomach to open into the cloaca or 

 median atrium on the dorsal side of the 

 body a little posterior to the ganglion. It 

 lies in that part of the body-cavity which is 

 included in the so-called gill. 



Plate xxxv of my memoir on " The Genus Salpa " is a median longi- 

 tudinal section of an advanced embryo of 5\ pinnata, showing the gill, g, 

 between the pharynx, which is colored red, and the cloaca, which is colored 

 green. The intestine, p, is shown in its place in the cavity of the gill, while 

 the anus, p', opens into the cloaca. The relation of the intestine to the gill 

 is also shown in S. pinnata in figures I, 2, and 3 of this memoir. Figure 7 

 of plate 2 of this memoir is a side view of an advanced embryo of 5*. flori- 

 dana, showing that the relation of the intestine to the gill is the same as it 

 is in the other cyclosalpas. 



8 1 



i3 



FIG. i. The solitary Salpa pin- 

 nata in ventral view. 



