234 GILBERT C. BOURNE. 



^•lycerine, whicli rendered the test trausparent and exposed 

 clearly the intestine, the atrial aperture^ and the other struc- 

 tures shown in Fig. 1. Further examination left no doubt 

 that the animal was an Ascidian. 



As I was unwilling- to destroy the single specimen, I 

 attempted to work out its anatomy by dissection, and with 

 this object in view I made a longitudinal incision in the test, 

 as shown in Fig. 3, and afterwards cut through the body just 

 below the circumoral arms in order to study the latter struc- 

 tures ; but the tissues proved to be so brittle and fragile 

 after long immersion in spirit that I abandoned any further 

 attempt at dissection, and embedded the two parts into which 

 the animal was divided in paraffin. A series of sections was 

 cut and stained with borax carmine, followed by picro- 

 nigrosin or picro-indigo-carmine. Though the epithelia were 

 in many places detached or peeled off from the underlying 

 tissues, the general histological preservation was good^ and 

 in most cases the cell elements, even of the fragmented 

 epithelia, were remarkably Avell preserved. I have therefore 

 been able to make a tolerably exhaustive study both of the 

 anatomy and histology of the animal, but before going into 

 details I will define the genus and species. 



Family Molgulid^. 

 Oligotrema, nov. gen. — Body sack-shaped ; the branchial 

 and atrial apertures distant; the branchial aperture terminal, 

 large, transversely elongated, surrounded by a circlet of six 

 muscular, pinnate arms or tentacles. The atrial aperture 

 minute, without lobes, placed on a small papilliform eminence 

 of the test near the hinder end of the body on the dorsal 

 side. The branchial sack much reduced and confined to the 

 anterior third of the body. 



Oligotrema psammites, n. sp. 

 With the characters of the genus. The test thin, but 

 tough, translucent ; its whole surfuce covered with hair-like 

 processes, to which sand-grains are attached; these capilli- 



