PLATE XI. 



Development o/Decapoda, continued. Fir/ures from N. Bobretzkt, Walter Faxon, Paul Mater, 

 Fritz Muller, Carl Glaus, and Fekd. Richters. 



1-9. Palmmon. From Bobretzky, Kl aMBPIOJOriH I.IEHnCTOHOrilX'L. 3annc. KieBCKaro OomecTsa 

 EcTeCTBOUcnbiTaTejieii, III., T. IV., V., VI., 1873. [On the Embryology of Arthropod.s. Mem. Kiel!' 

 Naturalists' Sou., III., PI. IV., V., VI., 1873.] 



1. Egg undergoing cleavage, superficial view. The cleavage is regular. Whether the first clefts reach the centre 



of the yolk or not Bobretzky was unable to determine, owing to the imperfection of his sections. At any 

 rate the deutoplasm soon invades the core of the egg to such a degree that the subseq^uent clefts do not 

 attain to the centre, and the segmentation becomes superficial. 



2. Section of later stage of the cleavage. The cleavage ]]roducts now have the form of long pyramids whose 



apices are fused in the deutoplasmic mass in the centre of the egg. The clear protoplasm, involving the 

 nuclei, has collected at the bases of the pyramids. Later the boundaries of the pyramids become obliterated, 

 while their protoplasmic bases become separated from the deeper food-yolk and form the cells of a superfi- 

 cial blastoderm. 



3. Gastrula s-tage, superficial view. 



4. Gastrula stage, section, b I, epiblastic layer, h y, hypoblast, djj, deutoplasm. 



5. Section showing the closure of the blastopore or gastrula mouth, m s, mesoblast, originating from the walls 



of the gastrula cavity. 



6. Nauplius stage, /ft, labrmn. n i, abdomen. I, first antenna. II, second antenna. Ill, mandible. ^)/, pro- 



cephalic lobe. 



7. Longitudinal section through nauplius stage. The hypoblast cells have increased and passed into and absoibed 



the whole yolk, forming a solid mass of hypoblast in which the outlines of the cells are almost obliterated. 

 pd, invagination of epiblast which forms the liind-gut. s d, invagination of cpiblast which forms the fore- 

 gut (oesophagus and stomach), a, tail fold, between which and the proctod;eum lies the ruilimentary abdo- 

 men. I b, labrum. 



8. Superficial ventral view of embryo at a later stage. The maxillte (IV, V) and maxillipeds (VI, VII, VIII) are 



seen as bilobed buds, cp, fold which forms the carapace, o c, eye, formed in the procepihalic lobes. 



9. Longitudinal section of late .stage in the development of the embryo. A portion of the nuclei of the hypoblast 



cells have migrated to the periphery of the yolk, and the cells have assumed a pyramidal form, similar to 

 the cleavage pyramids in Fig. 2. The protoplasm segregates in the bases of the pyrandds, while their ajiices 

 become lost in the central deutoplasmic mass, in which all trace of nuclei has disajipeared. The wall of the 

 mesenteron thus comes to form a single layer of pyramidal cells enclosing, and merging into, a central mass 

 of food-yolk. The protoplasmic ends of the hypoblast pyramids finally sejiarate as cellular layer, wliich 

 forms the lining of the mid-gut and liver in the adult. Connection is formed first with the proctodipuni, or 

 hind-gut, and later with the stomodoeum (cesophagus and stomach). The latter connection is not nia<le until 

 all the food-yolk in the mesenteron has been absorbed. )i, ventral nerve cord : »', supra-cesophageal nerve 

 ganglion. These originate from the epiblast ; the latter from the procephalic lobes. /(, heart arising in the 

 mesoblastic tissue. 



