1916] The Ottawa Naturalist 83 



affording one of the distinctions between plants and animals, 

 but this outer coat of the Ascidians is an animal product, 

 though not more essentially a part of the Tunicate's body than 

 the shell of an oyster or clam. A thin epidermis covers the 

 tunic, in which pigmented cells occur, and these migrate into 

 the tunic itself and impart to the animal its colour, which is 

 very brilliant and striking in some Ascidians. 



A few words only can be added about the life-history and 

 development of Tunicates. Eggs and sperms are produced by 

 the same individuals, though some are protandric, and do not 

 produce eggs until after the sperms are ripened; but budding 

 also occurs, and reproduction by stolons, a peculiar phenomenon. 

 From the egg issues a larva, very like a tadpole, the enlarged 

 head of which possesses several sticky papillae for the purpose 

 of adhering to external objects. A strong muscular tail per- 

 mits it to progress actively through the water. A rod passes 

 down the centre of the tail composed of a row of cells at first, 

 but later by the coalescence of these cells, it appears as a clear 

 hyaline resistent rod, or axis, representing the notochord or 

 primitive backbone of all higher animals. This first indication 

 of a vertebral column is a profoundly interesting feature in Tuni- 

 cates. Hardly less interesting are the larval organs of vision 

 and hearing, though, like mythical Cyclops, there is only one 

 eye, and the ear or otocyst is unpaired. Some Tunicate larva? 

 secrete a clear gummy blanket or floating house, and live in 

 it for a time, at the sea's surface. Oikopleura does that. 



It is unnecessary to describe subsequent changes further 

 than to say that, at a certain stage, the wriggling tadpole be- 

 comes rooted by its mouth-end to rocks or other objects, loses 

 its tail, its eye, its ear, and other organs, and becomes changed 

 into a leathery sac-like creature, sightless and motionless, the 

 typical rooted Ascidian, such as those Dr. Huntsman describes. 

 There are three main types among the Tunicates, viz. : the 

 Ascidiaceae, the Thaliaceae, and the Larvaceae, and over one 

 hundred genera. A promising field waits investigation, and Dr. 

 Huntsman's additions to our knowledge proves what a great 

 opportunity for scientific discovery young Canadian workers 

 have who resort to our three Government biological stations 

 each summer. The Tunicates offer a fruitful field for re- 

 search. Science has revealed unexpected marvels in the study 

 of these lowly-looking Tunicates, but while they are degenerate, 

 as a class, they appear undoubtedly to have formed the starting 

 point whence higher animals have evolved, and have progressed 

 in an ascending scale until Man, the highest Chordate or Ver- 

 tebrate, developed. 



