4 o DISCOVERY REPORTS 



Colony (Text-fig. 5 A). Most of the colonies in the collection show the characteristic shape of a 

 stout club or cone attached by the narrow end. They reach a height of 4 cm. The specimens do not 

 show the blue coloration which gives the species its name; Hartmeyer (191 1) also found that much of 

 his material was not blue, but van Name (1945) mentions the colour as being characteristic of most 

 material. The superficial layer of the common test is firm and is impregnated with sand grains, but 

 the test within the colony has no sand and is soft and clear, this being the usual condition in the 

 species. Sand is also lacking immediately round the oral openings of the zooids and round the margin 

 of the common cloacal opening. The zooids are arranged in a single peripheral layer with their oral 

 openings forming a ring round the upper part of the colony, slight swellings marking the position of 

 the zooids. The zooids number up to fifteen in a colony. 



Zoom (Text-fig. 5B). Table 8 shows the principle characters of the zooids of the 'Discovery' 

 specimens compared with those described by Sluiter (1906), Hartmeyer (191 1) and Kott (1954). 



Atrial languet 

 Oral tentacles 

 Stigmata 



Stomach 



Larva 



No. of larvae per 

 breeding zooid 



Table 8 



' Discovery ' 

 3-lobed 



Sluiter 

 Toothed 



20 



20-30 



8 rows, each crossed 10 rows 

 by a parastigmatic 

 transverse bar; or 

 16 rows without bars 



10-13 low folds 

 sometimes broken 



8 entire folds and a 

 few short ones 



1-11 



4 or 5 



Hartmeyer 

 3-lobed 



? 



No true folds ; in- 

 stead pigmented 

 lines 



Trunk i-omm. long Trunk 1-2 mm. long ? 



4 or 5 



Kott 



3-lobed 



16-20 rows, the anterior rows 

 with parastigmatic trans- 

 verse bars 



Smooth externally; intern- 

 ally with papillae some- 

 times arranged in rows 



Trunk i-o mm. long 

 (measurement taken from 

 fig. 66, Kott) 



? 



Thorax. The branchial sac is of a kind unusual in Aplidium in that parastigmatic transverse bars 

 (p.b.) are often present. These cross all the rows of stigmata in some of the 'Discovery' specimens, 

 but in others are entirely absent. As specimens with parastigmatic bars have only half the number of 

 rows possessed by specimens lacking the bars, it is evident that each row crossed by a bar is later 

 divided into two rows. This accounts for the large range in the number of rows. It may also explain the 

 fact that Sluiter noted ten rows of stigmata but eighteen dorsal languets, the additional languets 

 presumably corresponding in position to parastigmatic transverse bars which may have been present 

 in parts of the branchial sac. 



Gut. The true structure of the stomach is by no means certain. Deep and well-developed folds are 

 apparently rarely or never present, and are sometimes represented by pigmented lines or rows of 

 internal papillae. In the 'Discovery' specimens the folds are usually undivided (Text-fig. 5B, St.), 

 but sometimes broken up (Text-fig. 5D). The anus is opposite the 5th row of stigmata. 



Gonads. The gonads have the position usual in Aplidium, but the testis follicles (t.) are crowded 

 together instead of being biserially arranged. 



Larva (Text-fig. 5 E). The larva, with a trunk 1 mm. long, is unusually large for species of Aplidium. 

 The papillae are not very widely spaced, and have stout stems. Four median ampullae (m.a.) are 

 present, and on each side lies a series of lateral ampullae (l.a.) which number six according to Kott 

 (1954), but are much more numerous in the ' Discovery ' specimens. The lateral ampullae are attached 





