Crustacea. 



6571 



and not upon the other is a question yet to be solved. For some few 

 weeks the ova are carried about by the parent, during which time the 

 embryo within developes itself and progresses in growth until it has 

 arrived at the form which is known as the Zbe. By some in- 

 stinctive consciousness, the parent now liberates the young from 

 the ovisac : this it does by rupturing the outer case, sometimes by 

 means of its feet, sometimes by pulling with its claws or nipper-formed 

 hands. The young baby is thus early and unprotected cast upon its 

 own resources in the wide world of waters, and soon no doubt large 

 numbers fall a prey to hungry enemies ; but a protecting Providence 

 watches over a favoured remnant, which grow, and thrive, and people 

 the ocean. 



Within a few hours the young Zoe throws off its first tunic, or as a 

 little child who saw an older specimen remarked, " pulls off its 

 clothes this is repeated in the earlier period of existence, something 

 about every week or ten days, but in confinement we have never been 

 able to get it to pass beyond the second moult. We have taken them 

 so frequently at different sizes that we think we are enabled to trace its 

 growth with but a small, or perhaps no, hiatus in its history : with each 

 moult the animal increases in size, then strengthens in its struc- 

 ture and developes its new growth, until it again throws off the 

 exuviae, and increases in dimensions; but with each progressive step 

 a change of form is visible : when it is born it has but two or 

 three swimming legs and a long tail; behind these swimming legs 

 small sac-like appendages are apparent ; these gradually increase in 

 size, and become the strong claws and walking legs of the animal, 

 while those which are first the swimming legs decrease in their relative 

 importance, and fold themselves up as protecting and supplying organs 

 of the mouth. 



These things are small, and the close observation of the microscope 

 is required to observe the facts. The growth of every part is progres- 

 sive, and, curious to tell, all those members and appendages con- 

 spicuous in the young lose their importance and become either obsolete 

 or of secondary value in the adult. In its youngest stage it is always 

 swimming and knows no rest, — its paddle-like organs never cease in 

 their vibration, — weeks pass away and there seems no wearying; 

 but the time comes when, casting off the tunic once again, the soft 

 and fleshy legs have progressed to a size sufficient to bear the weight 

 of the animal ; the skin then becomes impregnated with lime, and the 

 structure sufficiently strong for use. 



. The animal now is changed ; it is less a swimming creature, but 



