280 Transactions. — Botany. 



no satisfactory explanation has been given as yet. The transparency of the 

 bladder membrane, and the presence of long bristles or antennae, may induce 

 small aquatic animals to attempt the passage. Darwin suggests that "per- 

 haps small aquatic animals habitually try to enter every small crevice, like 

 that between the valve and collar, in search of food or protection.* I can 

 myself vouch for the inquisitiveness of many of the small Entomostraca, 

 those species particularly which, like Cxjims, are secure in a two-valved shell, 

 being the boldest in this respect. The bladders do not seem to digest their 

 prey, there being no glands for secretion ; and fragments of meat, etc., 

 placed in bladders, were foiind unacted on at the end of three days. It is 

 probable that the animals which force an entrance into the bladders become 

 asphyxiated, owing to the contained oxygen being all used up, and that, as 

 their bodies decay, the products thus resulting are absorbed by the various 

 processes on the walls. 



The bladders on our Stewart Island species — Utricularia vionanthos — are 

 somewhat different from any of the species described in Darwin's book. 

 They are almost circular in outline, and laterally compressed, and vary in 

 diameter from J^ to ^ of an inch. Eunning almost completely round them 

 is a well-defined vascular bundle (fig. 5a & b) the inner end of which forms 

 the thickened collar or neck, against which the valve closes, while the outer 

 and upper end is sometimes continued into a horn-hke antenna, or is 

 abruptly truncated. On each side of the entrance are the so-called " antennas," 

 which in this species are narrow at the base, and expand outwards in a pal- 

 mate manner, ending in numerous unicellular hair-like processes. That 

 portion of the bladder between the entrance and stalk by which it is at- 

 tached, is bordered by a flange or expansion of the cellular tissue of the 

 walls on each side. This, together with the overlapping antennae, forms a 

 sort of covered way to the entrance. There are no spines directed into the 

 interior of the cavity, as in U. neglecta, nor could I detect any glands, other 

 than the numerous quadrifid processes (fig. 6) with which the whole inner 

 surface is lined. The arms of these processes are nearly equal in length. 

 The outside of the bladders is covered with rounded pit-like cells, at the 

 junctions of many of the hexagonal cells of the parenchyma. 



The smaller bladders were usually semi-transparent and empty, but the 

 larger ones were mostly filled with dark brown or blackish material. This 

 seemed to consist of disintegrated animal and vegetable remains, most of it 

 destitute of recognizable structure, but containing Diatoms, Algse, etc., and 

 in many cases Entomostraca. All the larger bladders had from one 

 to as many as ten specimens of the common Entomostracan, Cyclops nova- 

 zealandlcB, sometimes quite entire, and at other times in fragments. A good- 



* Loc. cit., p. 409. 



