94 



MEDUSAE. I. 



figures found by the measurements. - - It will be observed that the number of tentacles varies fairly 

 considerably within one and the same group of size; thus in specimens, i6-2omm wide, there may 

 be 38 58 tentacles. 



Each of the radial canals carries only one gonad, completely encircling the canal without leav- 

 ing a ventral edge free. This will be seen from the textfigures 16 and 17, representing transversal 

 sections of male and female gonads. The section of the female gonad shows that the eggs are first 



developed in the middle part on both sides, whereas small, immature 

 eggs are still present in the dorsal and ventral parts. 



From the Faeroe Islands we possess a number of young speci- 

 mens. In the smallest specimens (diameter i 5 mm) the gonads are 

 spherical and placed near the middle of the radial canals; in a spe- 

 cimen 7 mm wide the gonads '(female) are oval, about iV 4 rnm long; 

 in the largest specimen (diam. 10 mm) they are elongate, 2 mm long. 

 Fig " l6 ' Fig ' I7 ' In all specimens from Iceland the gonads are linear. Their 



Fig. 16. Phialidium hemispluzricum (Gro- 



novius). Transversal section through length in relation to the length of the radial canals varies from '/, 

 radial canal with mature male gonads. 



- Fig. 17. Phialidium hemispharicum to nearly 3/ but stands in correlation to the developmental stage of 

 (Gronoviusl. Transversal section through 



radial canal with female gonads. the individual, as will be seen from table XII. This table represents 

 the correlation between the diameter of the individuals and the relative length of the gonads (i. e. the 

 relation between the length of the gonads and that of the radial canals, expressed by means of the 

 figure ). For each individual I have calculated with 2 decimals, and these figures have been used 

 for the calculation of the average numbers presented in the table. In the specimens examined the 

 figure - varies from 0.33 to 0.73. It will be seen from the table that up to a size of 6 10 mm in 



?* cr 



diameter the gonads have nearly the same relative length in both sexes ( = about 0.4), but during the 



Table XII. Relative length of gonads in specimens of different sizes of 

 Phialidium hemisphcericum from Iceland. 



Diameter 

 of individuals, 



- relation between length of gonads and 

 length of radial canals 



