PLATE IX. 



I - 10. Development of Schizopoda, continued (MysU). Figures from Edouard Van Beneden 



cnul P.-J. Van Beneden. 



1-6. Myis ferruginea. From fidouartl A'an Beneden. 1-3, Eecherclies .sur la Composition et la Signification 

 de I'CEuf, PI. X. Mem. Cour. Acad. Roy. Belgique, XXXIV., 1869. 4-6, Rerherches sur I'Erabvyo- 

 genie dcs Crustaces. II. Developpement des Mysis. Bull. Acad. Ro}-. Belgiijuc, [2.] XXVIII., PI. III., 

 1869. 



1. Egg showing the commencement of partial segmentation. 



2. Later stage in the segmentation. The Mastodcrm now forms a zone of small extent at one pole of the egg. 



3. The blastoderm has extended over the whole surface of the yolk. On the ventral side the cells have a roundish 



form, while on the dorsal side they are very much flattened. 



4. Later stage. 2' ^> anterior expansion of the ventral side of the blastoderm to form the procephalic lobes. 



a, fold of the blastoderm which separates the hinder portion (n h) of the embryo from the anterior section of 

 the body. 



5. Later stage. The embryo is now ready to leave the egg. The three nauplian appendages, two pairs of anten- 

 , nffi, and mandibles (I, II, III) are present, and the embryo is invested with a delicate cuticle. X, dor- 

 sal organ. While within the egg, it will be observed that the body has a ventral flexure, as in Decapod 

 Cnistacea. 



6. Embryo after it is freed from the egg-membranes. The body now assumes a dorsal flexure. 



7 - 10. Mysis chamceko. From P.-J. Van Beneilen, Reeherches sur les Crustaces du Littoral de Belgique. Mem. 

 AcVl. Roy. Belgique, XXXIII., 1860. 



7. It has been seen by the previous figures that the ifijsis embryo leaves the egg with three pairs of appendages 



like a nauplius. The larva undergoes its further development within the incubatory pouch of the parent. 

 The nauplius skin is not discarded, but accommodates itself to the growth of the larva, forming a protective 

 case, within which the yoimg Mysis develops. In the species here figured, the nauplius skin terminates in 

 a pair of setiferous appendages. Within the nauplius skin, the larva has become provided with the full 

 number of cephalo-thoraeic appendages in the form of simple buds. These afterwards assume the sehizopo- 

 dous character, the abdominal appendages appear, and the segmentation of the body sets in. 



8. Larva just after the nauplius skin has been cast off, much less enlarged than the preceding figure. The 



stalked eyes (o c) are now conspicuous. They have developed from the procephalic lobes of the embryo. 

 The fuU number of abdominal appendages (XIV -XIX) is now seen, the posterior pair largely developed. 



9. Later stage, shortly before leaving the incubatory pouch of the parent. 



10. Appendages from the first to the fourteenth (first abdominal) inclusive, to show the double nature of the 



appendages. 



11-21. Development of Peneus. Figures from Peitz Muller and Carl Claus. 



II - 16. From Muller, Die Verwandlung der Garneelen. Arch. Naturgesch., XXIX., Taf. II., 1863. 



11. Nauplius stage of a PfH.fi<«, from DcsteiTo, Brazih .4 mm. long. 



12. Older stage (metanauplius), seen from the side. .5 mm. long. The carapace [cp) has commenced, a large 



labrum (Ih) is present, together with the rudiments of four pairs of appendages (two pairs of maxillae and 

 two pairs of maxillipeds) behind the nauplian appendages. A short forked tail has also formed. 



13. Third pair of nauplius appendages of a somewhat older stage. At its base Is seen the rudiment of the masti- 



catory mandible of later stages. 



