. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 58 COPEPODA Introductory Remarks. The material which I have examined of this species has been very big, as it is one of the most abundant and widely distributed plancton-copepods of the northern seas; it was therefore quite necessary for me to try to solve the question, whether different or only a single species alike to Pseudocalaniis minutus exist; unfortimately the result of my investigations is not quite satisfactory. Sars has been the first, who has pointed out that different types exist, and taking the scanty material
. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 58 COPEPODA Introductory Remarks. The material which I have examined of this species has been very big, as it is one of the most abundant and widely distributed plancton-copepods of the northern seas; it was therefore quite necessary for me to try to solve the question, whether different or only a single species alike to Pseudocalaniis minutus exist; unfortimately the result of my investigations is not quite satisfactory. Sars has been the first, who has pointed out that different types exist, and taking the scanty material into consideration he was quite right in establishing the three species Ps. clongatus Boeck, Ps. major G. O. S. and Pseudocalanus gracilis G. O. S. No naturalist has later on tried to solve the question, scarcely touched it'; most of them have examined specimens from southern regions and '' have scarcely been wrong in referring them to the Ps. elon- gatus Boeck (sensu strictu). According to Sars the 3 species are characterized in the fol- lowing manner. i) Ps. major G. O. S. Aver- age length of $ 24 mm. Tlie head is only slightly produced anteriorly; the abdomen is half as long as the cephalothorax. The antennulae extend almost to the middle of the abdomen. 2) Ps. clongatus Boeck (sens, strict). The average length is 1-4 ram. The head is only slightly produced anteriorly; the urosome somewhat exceeding half the length of the anterior division. The antennulae scarcely reach beyond the second caudal somite. 3) Ps. gracilis G. O. S. Average length 1-65 mm. The body is more slender and the head anteriorly distinctly produced; the urosome scarcely exceeds half the length of the anterior division; the caudal rami are comparatively narrower and more divergent. The antennulae reach to the end of the third caudal somite. Legs considerably more slender than in the typical species, with both rami very narrow. It will be noticed that in most characters, except in size, the Ps. gracilis dif
Size: 2079px × 1202px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectscienti, bookyear1915
