ii6 Transactions of the Canadian Institute. [vol. ix 



at some distance from the atrial siphon, where the current is not as great 

 and as a result the eggs are usually retained. This retention of the eggs 

 may be quite constant in a genus, may be characteristic of certain 

 species only of a genus, or may occur only in occasional individuals of a 

 species. In some cases the eggs are, though retained, laid in lots, so 

 that practically only one stage can be obtained from one individual 

 and all the individuals of one locality may have their eggs at the same 

 stage of development. The following is a list of the simple forms of 

 the stations that retain their eggs: — 



Genera — Dendrodoa, eggs produced continuously. 

 Katatropa " 



Species, — Caesira cooperi, eggs produced continuously. 

 C. canadensis, " " " 



C. littoralis, 



Occasional individuals of 



Ascidiopsis prtmum, eggs produced in lots. 

 Corella inflata, " " " 



Boltenia hirstUa, (?) 



Young individuals, for studying the post-larval development, can be 

 obtained in the case of the commoner species by carefully examining the 

 free surface in individuals of those species which have a roughened test. 

 Individuals, that were anaesthetized with cocaine, killed in the extended 

 condition and well fixed, have furnished me with an abundance of stages 

 of some of the commoner species. A series of sections made of an adult 

 Dendrodoa carnea, yielded in addition, (i) an almost complete series of 

 stages of the same species from the fertilized egg up to the free-swimming 

 larvae, (2) a 'young adult* of the same species, (3) two 'young adults' 

 of Ascidiopsis prununi and (4) a ' young adult ' of some species of Caesira I 



As is well known, the Ascidians harbour many commensals. Pro- 

 tozoa are to be found in the pharynx and atrial cavity in many of the 

 simple forms of both coasts, the majority being attached to the oral 

 tentacles. Various kinds of Copepods and Amphipods are to be found 

 in the same cavities. Pea-crabs occur in the atrial cavity in most speci- 

 mens of Tethyum igaboja, Ascidiopsis paratropa and Phallusia ceratodes 

 of the West Coast. A hydroid* is abundant at Departure Bay, coating 

 the prebranchial zone of certain species of Ascidians and small colonies 

 were occasionally found on the wall of the atrial cavity. Nearly every 

 individual of Phallusia ceratodes contained this form and it was also found 

 in Ascidiopsis paratropa, dona intestinalis, and Tethyum aurantium. 



*Mr. C. McLean Fraser has recently described this form (Bull. Lab. Nat. Hist. Univ. 

 Iowa, vol. VL No. 1) as the type of a new genus, belonging to the family Turridae. 

 He has given it the name Crypta huntsmani. 



