DESCRIPTION OF SPECIES 141 



External appearance. This well-known species requires little additional description as regards 



external form. The smallest specimen in the collection is i-i cm. long and the largest 23-0 cm. 



Several specimens give no evidence of attachment other than the presence of sand on the test, but in 



some a number of small pebbles are embedded in the test of the lower part of the body, suggesting 



that in life these animals were thus anchored to the bottom. 



Internal structure. This also has been well described by a number of authors (see especially 



van Name, 1945). The individual variation in the branchial sac, intestinal curvature, and position of 



the left gonad in the species are such as to include the characteristics of form capax Arnback (1938). 

 Biology, (a) Breeding. The annual breeding cycle has been determined by examining all specimens 



and estimating the state of the gonad, which has been classified as 'full', 'spawning' or 'empty'. 



NUMBER OF 

 SPECIMENS 



□ 



EMPTY 



PARTLY EMPTY 



FULL 



VII 



MONTHS 

 Text-fig. 63. Paramolgula gregaria Traustedt. State of the gonad in all specimens, in all years, 



in relation to the month of the year. 



These groupings refer to the ovary ; ' spawning ' means that an appreciable quantity of eggs has been 

 shed from the ovary and the specimen has evidently been taken during its female-spawning period. 

 Animals under about 3 cm. have not been included as they had not yet attained sexual maturity. 

 Text-fig. 63 shows the reproductive state of all animals over 3 cm. long. It seems that most of the 

 spawning takes place in the months of February to May, that the animals are spent during the southern 

 winter, and that the gonad becomes active again in November. No material was available from the 

 months of August and September. 



(b) Food. Specimens were examined from material collected at different times of the year. In all 

 of these there was food in the gut, and at all seasons the food consisted largely of unicellular planktonic 

 algae, mainly under 20 fi in diameter. Diatoms were also present, but less abundant. Occasionally 

 parts of Crustacea (amphipods and copepods) were found, and it seemed that these were either alive or 



