MOLLT7SCA. 171 



Order I. BIPHOKA. 

 THALIA. THALIACEA. T^ENIOBRANCHIATA. MONOCHITONIDA. 



Outer and inner integuments united throughout. Branchia 

 ribbon-shaped. An opening at each extremity. Free-swimming. 

 Sexes distinct. 



Salpidae were said to be solitary in one generation, which, by 

 gemmation, gave birth to a connected group in the next. This 

 was the ' ' simplest form " of the alternations of generations. But 

 it is now maintained by Brooks and Todare that the solitary and 

 the grouped individuals are the offspring of the same parent, the 

 former being the result of sexual reproduction (the female), 

 the latter of budding (the chain of males). Like the Pyroso- 

 rnatidas, they are brilliantly luminous. 



As individuals these animals are transparent, tubular in shape, 

 and when united form a long chain, sometimes called by seamen 

 " sea-serpents." On the west coast of Scotland they are occa- 

 sionally found in vast numbers ; at such times M'Intosh com- 

 pares the appearance of the sea to boiled sago, and Huxley 

 speaks of their masses through " which the voyager in the great 

 ocean sails day after day." 



Doliolidre are pelagic, and are represented by sexual and sexless 

 forms. They are transparent cask-shaped organisms, progressing 

 by contracting and forcing the water out at one or the other 

 extremity. The branchiae consist of ciliated tubular bars, di- 

 viding the respiratory sac into two chambers. 



Schmarda refers Appendiculariidas and Pyrosomatidse to this 

 order. 



Salpidcs. 

 Salpa= Thalia. Doliolum. 



Order II. ASCIDIOIDA. (Ascidians.) 

 ASCIDIACEA. TETHYONACEA. SACCOBRANCHIATA. CHTHONASCIDLE. 



DlCHITONIDA. 



A dilated pharynx performing the functions of branchise. 

 Outer and inner integuments only united at their apertures, or 

 by blood-vessels at a few other points. 



The pharynx acts as a respiratory organ as it passes the sea- 

 water and nutrient matter to the stomach ; it is " always exceed- 

 ingly dilated," and the sides more or less perforated. The entry 

 to this pharyngeal or " branchial " sac is occasionally guarded by 



