Egg Size, Nauplius Size, and Their Variation with Local, Geographical, and Specific Factors in Some Common Cirripedes

Abstract

Where possible the eggs, separated from the egg-masses, were measured fresh; when the material had to be preserved Gilson's fluid was used. This helps to break up the egglamellae and, if they are reasonably ripe, eggs are separated on gentle agitation. Ova were shaken out of the ripe ovaries and allowed to round off for 30 min before being measured. Nauplii were measured lying on their dorsal side; for stage I the total length from anterior to posterior and the greatest width of the carapace were measured. The measurements were made under a binocular microscope using a scaled eye-piece which was read to the nearest 0 5 division; the magnification was such that the eggs were about 40 scale divisions, with 1 division -6-0 It. When focusing problems on ellipsoid eggs at higher magnifications are taken into account a moderate magnification of this order seems adequate even though higher magnification may give an appearance of greater accuracy. Where possible at least 200 eggs, obtained by pooling aliquots from a number of individuals, were measured.