326 BULLETIN OF THE 



referred to. They relate almost exclusively to the intra-oval develop- 

 ment, and for this part of the history are the completest yet made, the 

 microtome having been used for getting sections of the egg in the differ- 

 ent stages of its growth. 



In 1874 Anton Stuxberg published an incomplete description of the 

 embryo before hatching, and of the first larval stage of Palcemon squilla* 



In an abstract of a paper on the development of Criostacea, by Spence 

 Bate, in the Proceedings of the Royal Society of London, 1876,t (the 

 full paper has never been published to my knowledge), the author makes 

 the surprising statement, that in the embryo of Palcemon, etc., the 

 anterior of the three earliest formed pairs of lobes (nauplius -appendages) 

 develop directly into the eyes, while the posterior two pairs are cast off 

 with an early moult and replaced by the permanent antennae ! 



Cambridge, June 1, 1879. 



* Karcinologiska iakttagelser. Ofversigt af KongL Vetenskaps-Akad. Forhandl., 

 1873, No. 9, pp. 16 - 19. 1874. 



+ "On the Development of the Crustacean Embryo, and the Variations of Form 

 exhibited in the Larv<B of 38 Genera of Podophthalmia," Proc. Royal Soc. London, 

 Vol. XXIV. pp. 375-379. 1876. 



I believe I have not misrepresented Spence Bate here, but will quote in full : — 

 " The author has taken this opportunity of making a close examination into the 

 earlier stages in the development of the embryo, and comparing the progress within 

 the ovum of some of the larvae that arrive at or near maturity before being hatched, 

 with those of the larval forms that are hatched in a more immature condition ; and 

 he states that, as soon as the protoplasm assumes anything like a definite plan, dis- 

 tinct lobes, corresponding in position with those of the several appendages in the 

 Nauplius, together with an embryonic or ocular spot, are present ; that in the 

 Nauplius forms they exist as deciduous appendages only, and are soon cast aside 

 and replaced by others more adapted to the wants of the adult existence. 



"In the embryos of other Crustacea the anterior pair of lobes enlarge in size 

 with little alteration of form, while the posterior two pairs are developed into 

 appendages that have but a deciduous value, since they never fulfil the office of 

 permanent organs, and are generally cast off with an early moult. 



"This is observable within the ovum in Palcemon, Crangon, etc., and also in the 

 marsupial embryo of Mysis after it has quitted the ovum. 



"The relation of these parts to the permanent organs the author has closely 

 traced, and believes that he has demonstrated that the three pairs of mobile append- 

 ages in the cirripedal or Nauplius fonn of larva homologize with the eyes and two 

 pairs of antennae, and not with the antennae and mandibles, as stated by Fritz 

 Miiller, Anton Dohrn,and others." 



