are, what Bate and Westwood have already hinted at, in their 

 highest and most advanced stage ; the organs of sense and mo- 

 tion being proportionately larger and better developed at that 

 period of their existence than ever after. In this free stage the 

 young get their aeration through the entire integument. I sup- 

 pose that after the brood of larvae have left the marsupium of the 

 female, they will actively swim about in the sea, attaching them- 

 selves, if possible, to egg-clusters of female prawns; 1 with the 

 young of the latter they simultaneously grow up, and enter 

 their branchial cavity in pairs at an early period of life. 



In June, 1881, I found a few (out of several hundred) live 

 females with males, the former with empty marsupia, which fact 

 led me to believe that this Bopyrus may produce more than one 

 brood, but the few cases may either be exceptions or, what is 

 more likely, the broods had just left their marsupia, leaving the 

 parents to their fate. 



The following observations were made on the eggs and em- 

 bryos taken from the marsupium of live female specimens. The 

 specimens were obtained during May, June and July this year 

 (1881), and the number of more advanced developmental stages 

 was not at all augmented in the latter month, nor was this the 

 case with a lot received late in August. By far the greater num- 

 ber of prawns, regardless of sex,' 2 exhibited through their trans- 

 parent carapace the yellowish eggs of the female Bopyrus, nearly 

 all, with but a few exceptions, showing under the microscope the 

 peripheric blastoderm cells within which a larger or smaller, en- 

 tire or subdivided yolk-mass could be distinguished (see PI. 1, 

 fig. 1). The few exceptions just mentioned showed, when viewed 

 from the side, the budding limbs and segments very indistinctly, the 

 two body-ends however, head and tail (pleon) being more dis- 

 tinct, exhibiting the form seen in PI. 1, fig. 3. Those prawns 

 which showed through their swollen carapace a more grayish 

 mass, contained the Bopyrus embryos invariably in their larval 

 skin, a drawing of which is seen in PI. 1, fig. 2. 



These embryos contained a central undifferentiated yolk-mass, 

 with a few yellow oil-globules and some larger orange-colored 



1 Bate and Westwood, p. 217. 



