276 NOTES <>N lioPYRUS SQUILLARUM. 



excrescences on the under side margins of the tail. Beneath 

 the plates covering these the male is usually found. Fig. 4 

 exhibits the male in situ. The colour of the female Bopyrue 

 is pale green, and the body is not of strong consistence. The 

 young Bopyri are of an oval form, somewhat like a wood 

 louse, with the outer pair of antenna) greatly elongated, carrying 

 slender setae. The legs are sub-chelate, and the tail carries two pairs 

 of joints, terminating in Betffl. It appears that in the nauplius or 

 larval condition (Fig. 5), the young exhibit the most advanced sta.^e 

 of development; according to Spence Bate and Westwood, "the 

 organs of sense and motion being proportionately larger and better 

 developed at that period of their existence than ever after." Messrs. 

 Spence Bate and Westwood further say : " It would thus appear as if 

 the nervous energy was then greater, and that the growth of males 

 and females is but what Dr. James D. Dana calls a vegetative process, 

 and one that is destructive of capitalisation, which decreases in 

 proportion to the growth of the animal. They therefore argue 

 that of the adult Bopyri the smaller male ought to be taken as typical 

 of the species rather than the more abnormal female." I particularly 

 direct your attention to the fact of high development in the nauplius 

 stage as a most remarkable illustration of that special branch of 

 modern biological speculation termed phylogeny, which professes 

 "that the development of any organism should furnish the key to its 

 ancestral history."* It would appear from this that Bopyrus is derived 

 from some more perfect form of crustacean, and that its degraded 

 organs in the female in maturity are due to its peculiar environ- 

 ment within the carapace of the prawn. The Bopyri seem to gain 

 access to the body first by sheltering in the early stage among the 

 freely hanging ova of the prawn. They work in pairs, as appears from 

 a communication to the Proc. Zool. Soc, November 24, 1863, after- 

 wards finding their way into the carapace, and so, as the authors I 

 have quoted say, " having quitted the care of their own parent they 

 are fostered by another on whom probably at a later period they prey 

 parasitically." As with most parasites the fecundity of these 

 creatures is considerable, no fewer than 800 young being nourished in 

 the incubatory pouch of the female. Most of these perish, for only 

 one mature parasite and its mate iufest their host at one time. 



The existence of Bopyrus has been known for some time, but not 

 properly understood; for in the year 1772 Mous. deBondaroy, a French 

 naturalist, published a memoir on Bopyrus squillarum disproving the 

 old fallacy entertained by fishermen on the coasts of France that 

 Bopyri were the young of soles or other fiat fish, which took shelter 

 under the shell of the prawn to protect them in their early stages of 

 growth — an idea held even by some scientific men at that period. In 

 the year 1837 Hathke made some interesting observations upon 

 Bopyrus, showing from an examination of a number of specimens that 



* Huxley. " Manual <>i [nvertebrata." Introduction, pa^r n. 



