1896 NOTES AND COMMENTS. 87 



ments, Mr. Groom remarks that most authors have transposed the 

 dorsal and ventral surfaces, and that the whole account of embryonic 

 development has been thus thrown into great confusion. The reason 

 he assigns for the mistake is that the appendages appear first on the 

 dorsal side of the embryo. " It is only, however, the free ends which 

 are thus seen, the main part of the appendage being applied to the 

 sides of the body, and the origin, as usual among appendiculate 

 animals, ventral." It appears almost certain, he adds, that in 

 copepods, as well as in cirripedes, " the surface of the embryo, on 

 which the median longitudinal and transverse furrows appear, and 

 which has been described as ventral, is in reality dorsal." 



On the stimulus of light, Mr. Groom refers to experiments upon 

 the Nauplii of Balanus perfovatus, from which he and his colleague, 

 Dr. Loeb, inferred "that light of sufficient intensity and duration 

 ordinarily causes them to turn the oral lobe away from the light, 

 while weaker light has after a time the contrary effect." He has 

 probably not seen the criticism by Dr. Giesbrecht(" Pelagische Cope- 

 poden," p. 807), that the authors have misapprehended the distribution 

 of light in a cylindrical glass filled with water, and illuminated from 

 one side only, in which they have supposed that to be the darkest part 

 which is really the most brightly lighted. 



In a second paper (Quart. J own. Micr. Sci., vol. xxxvii., pp. 269- 

 276) Mr. Groom passes to the latest nauplian stage, having had the 

 opportunity of observing this metanauplian or immature Cypris-stage 

 in a species of Balanus from Jersey. Professor Chun, on his part, 

 has had the means of describing the metanauplian stage in two 

 species of Lepadidae. A little earlier Dr. Aurivillius published some 

 remarkable facts as to the post-embryonal development in various 

 species of Scalpellum. Here the metanauplian stage of the young 

 was found within the capitulum of the mother, leading to the 

 inference that, instead of half a dozen free nauplian stages, in these 

 instances there is an abbreviated course of development, with none 

 of the nauplian stages free. 



In regard to the food of the Nauplii, Professor Chun testifies to 

 finding in the intestines needles of Radiolaria, well-preserved skeletons 

 of Dictyochse, carapaces of diatoms, and remnants of Globigerinae. 

 He considers the bristles of the appendages well adapted for the 

 ingathering and sieve-like retention of particles of food. Some of the 

 long spines, armoured and glandular, are admitted to be weapons 

 offensive and defensive. But on the whole he thinks that the rich 

 apparatus of elongate spines and plumose bristles is chiefly subser- 

 vient to flotation. 



Two points in Dr. McMurrich's essay must be mentioned for the 

 bearing they appear to have on the question now under debate of 

 separating the tribe Chelifera from the Isopoda. Dr. McMurrich 

 confirms the observation by Nussbaum (1891) that there is a transitory 

 exopodite on the thoracic appendages in the embryo of Ligia, and 



