266 



KNOWLEDGE. 



[Decembee 1, 1900. 



THE KARKINOKOSM, OR WORLD OF 

 CRUSTACEA. 



By tlie Rev. Thomas R. R. Stebbing, m.a., f.k.s., f.l.s., 

 F.Z.S., Avthor of " A History of Cruatacea," " The 

 Naturalist of Cumhrae," " JRepnrt on the Aniphipoda 

 collected by H.M.S. ' Challenger,' " etc. 



CRUSTACEAN NURSERIES. 



To be rocked in (lie cradle of the deep is tlie lot of 

 many juvenile crustaceans, and, however forlorn it may 

 sound, it exactly suits their constitution. So long as 

 the brood remain attached to the mother's body, on 

 ti-unk or pleon, on back or front, in pouches or free, in 

 irregular masses or shapely packets or long pendant 

 strings, varying an-angements of the maternal organism 

 or mode of life provide for their health and welfare. 

 But upon detachment, whether before or after hatching, 

 the young pass out of the mother's care. Sometimes 

 the separation takes place under such circumstances 

 that the mother is sure to be dead before the birthday 

 of her offspring arrives. Obviously in the intemiediate 

 period they cannot maintain any active struggle for 

 existence. Many no doubt succumb, without ever a 

 chance of climbing up the climbing wave, but quite 



diately closes." Since the mother herself is only a 

 sixtieth of an inch in diameter, how powerful a micro- 

 scope must Pritchard have used that could not only see 

 into the maternal consciousness, but could also discern 

 that the infants were " playing," that they had a sense of 

 approaching peril, and that they knew where to flee 

 for refuge ! It is odd that the reciprocal affection thus 

 pleasingly described should find no authentic counter- 

 part in the highest ranks of the Crustacea, in which they 

 might have been perceived with some less exceptional 

 instniment. The West Indian land-crabs must be far 

 above any entomostraca in intellectual development, and 

 they lay their eggs in the sea, thus leaving their young 

 ones in a very literal sense to fish for themselves. 



We speak of children as little men and women, and 

 of men and women as children of a larger growth. 

 Between cats and kittens there is a very close resem- 

 blance. People have been known to eat lamb niistaJfing 

 it for mutton. Therefore, when an amphipod comes out 

 of the egg a meek and miniature copy of its mother, 

 that seems to be an ordinai-y and regular sort of per- 

 formance. When a young woodlouse is born, a casual 

 observer might think it a little off colour, but would 

 probably deem it much like its parents in isopodan shape 

 and structure, overlooking the absence of its last pair of 



A. B. c. 



Qnaihia inaxillaris (^iloniagw). From Sars. A, Male ; B, Larva- C Female. 



enough survive, sheltered in safe inglorious mud, to 

 become portions and parcels of the fateful future. 

 Sometimes the young have habits quite different from 

 those of their parents and of necessity live apart. Even 

 where the display of maternal care and affection is 

 not physically impossible, it can be little needed in this 

 extremely prolific class of animals, and the records of 

 it, which are partly discredited by their rarity, cannot 

 be accepted without corroboration. There is the little 

 globular entomostracan Chydorus sphaericus (Miiller), 

 of which Dr. Baird says, " According to Pritchard, the 

 young play near their parent, and at the approach of 

 danger swim for protection within the shell of the 

 mother, which she, conscious of their feebleness, imme- 



legs or reckoning the want of two legs out of fourteen 

 a trivial aritlnnetical detail. Nevertheless between the 

 young and adult of a crustacean species there is some- 

 times so gi-eat a difference that science has long stumbled 

 and stammered before recognising the relationship. To 

 rear a species from the egg to maturity, under obser- 

 vation in an aquarium, may seem a facile method ior 

 dealing with any such questions of affiliation. The mis- 

 fortune is that the foundlings to be operated on are 

 in their early youth often of a very delicate constitution. 

 Each moulting which leads them out of one shape 

 into another is a crisis in their existence. Those who 

 bring them up by hand must find out what temperature 

 of the water they require, what amount of movement 



