ECOLOGY AND TAXONOMY OF HaUmeda 51 



conditions occur in other species where the calcium carbonate deposits 

 do not extend as completely to the surface and some of the utricles are 

 slightly attached to each other. 



An illusion of roundness seems to be produced by preparations from 

 a few species, especially gracilis and lacrimosa. However, by focusing 

 up and down with the microscope, very faint hexagonal lines can 

 generally be observed (Hillis, 1959). The appearance seems to result 

 both from the slightly convex outer surface of the peripheral utricles 

 and by adjacent utricles touching only very slightly. 



There are other variations. The walls appear somewhat thicker in 

 stuposa and cylindracea for example (Hillis, 1959), and in velasquezii 

 and cylindracea the "covering lamella" (Section I) of the outer surface 

 of the peripheral utricles (Taylor, 1962, for velasquezii; Borowitzka and 

 Larkum, 1977, for cylindracea; both using the term "cuticle") appears 

 to be more prominent than in some other species. This may also vary 

 with condition of the material. 



Yet another variation occurs in cuneata, discoidea, gigas, taenicola, 

 tuna and sometimes other species, in the occasional lateral fusion of 

 adjacent utricles in twos, threes and rarely fours (Fig. 17, Nos. 11, 12; 

 Fig. 20, Nos. 5, 11). This fusion is distinct from adhesion, the usual 

 pattern, where the utricles retain their individual walls. 



(iv) Lateral adhesion of adjacent peripheral utricles. Longitudinal 

 sections (Subsection 2.b.iii) are required to observe this character. 



Adjacent peripheral utricles usually adhere where they touch. In 

 cylindracea, and very possibly all of the species, this appears to be 

 brought about by the fusion of the covering lamellae of the participating 

 utricles (Borowitzka and Larkum, 1977). The remainder of the filament 

 walls in the region of contact generally retain their distinctiveness, 

 although there are exceptions as noted in Subsection (iii). 



The extent, or length, of the adhesion ranges from none (macrophysa, 

 fragilis and often favulosa) to about half their length [cuneata and 

 discoidea; Fig. 20). In lacrimosa and gracilis it is restricted to a thin 



distinct utricles (are utriculiform) ; but in species of section Opuntia and a 

 few other species the utricles, formed by dichotomous branching, are not swollen 

 or specialized, and hence appear like regular branch&s. This type of cortical develop- 

 ment is shown in Nos. 1. 2 and 6. 



(1) H. fragilis; (2) H. micronesica ; (3) H. bikinensis; (4) H. scabra; (.5) H. gigas; 

 (6) H. opuntia; (7) H. tuna; (8) H. macrophysa; (9) H. gracilis; (10) H. cuneata; 

 (11) H. discoidea; (12) H. lacrimosa; (13) H. lacunalis; (14) H. taenicolu; (15) H. 

 simulans; (16) H. m,onile; (17) H. macroloba; (18) H. stuposa; (19) H. cylindracea; 

 (20) H. favulosa; (21) H. incrassata. The long scale applies to No. 6; the short scale 

 to the others. (Adapted from Hillis, 1959.) 



