XXXVI1 INTRODUCTION. 
assists in lubricating the branchial plates in warm and 
strongly evaporating atmospheres. We have been led to 
this conclusion from finding that they diminish in size in 
those specimens that have been long detained in dry 
places 
GENERATION. 
The organs of generation in the male of the Sessile- 
eyed Crustacea are not to be determined without great 
nicety in dissection and care in manipulation. We have, 
however, in Sulcator among the Amphipoda, and Ligia 
among the Isopoda, been able to examine them clearly, 
besides less perfectly so in the animals of other genera in 
both orders. Bruzelius and Loven have given their atten- 
tion to the former order, and demonstrated the arrange- 
ment in the genera Gammarus and Podocerus. The male 
organs internally consist of a more or less oblong pair of 
testes, which are liable to vary somewhat in form in 
different genera. These testes are fitted with numerous 
small seminal cells. A narrow passage, or vas deferens, 
connects this organ with a second oval chamber, or 
vesicula seminalis, which is filled with long fine hair-like 
spermatozoa, lying thickly coiled one upon another. 
From the vesicula seminalis a narrow passage leads to the 
inner surface of the first joint of the seventh pair of legs, 
where it penetrates in each into a soft membranous 
external penis. We have kept species of Amphipoda long 
under observation, and paid close attention to their habits, 
but have hitherto failed to detect any communication 
between the sexes which would admit of a direct passage 
of the penis into the vulva of the female. 
The male Amphidod grasps the female by one of its 
strong subcheliform gnathopoda, inserting its claw 
beneath the anterior edge of the first segment of the 
