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Development of the Decapods. When we come to the stalk-eyed 

 Crustacea, such as the shrimps and crabs, we are introduced to 



phosis, as first shown by Thompson. The life-history "of a Deca- 

 pod is full of interest and significance, as the phases which some 

 present from the larval stage up are as varied and astonishing as 

 the biography of any animal known. In the group as a whole, 



great detail and complexity of form, the animal -hitting its garb 

 as if an actor with many parts to perform in the drama of life, 

 while in its co-species these phases may be mostly suppressed, and 



the narrow compass of the ('.'--shell. 



One Decapod, the shrimp Penams, studied by Fritz Midler, on 

 the coast of Brazil, is an exception to all other stalk-eyed Cms- 

 life. On the other hand, there is the common lobster, or fresh 



pressed, under-one in the eg- and uhieh hatches in nearly or 

 quite a similar form to the fully grown animal. Between these 

 stages there are all grades in other Crustacea. 



species which undergo a metamorphosis, quite similar mode. 

 The yolk so far as known (Scyllarus, Astacus, etc.) undergoes 

 partial segmentation : no case of a total division is as yet known. 

 After the formation of a short round primitive streak, or band, 

 the limbs arise. In several cases observed by Dohrn, the three 

 anterior pairs of limbs, namely, the two antenna} and the mandi- 

 bles were developed simultaneously and before the others appear. 

 The embryo may with truth, then, as Dohrn states, be said to pass 



passes through a iNh-like -tag.-. He observed this nauplius-stage 



