150 MCMURRICH, 



EXPLANATION OF PLATE VIL 



Fig. 37. Embryo of Asellus represented as spread out flat. 



Fig. 38. Embryo of Aselliis in stage later than Fig. 37 showing the teloblastic 

 growth of the meta-naupliar portion. 



Fig. 39. Ovum of Porcellio in the one-celled stage. The thickness of the 

 peripheral protoplasm (//>) in this and the next figure is slightly exaggerated. 



Fig. 40. Ovum of Armadillidiiim in the two-celled stage. 



Fig. 41. Four-celled ovum of Arrnadillidiiun. 



Fig. 42. Section through a four-celled ovum of Porcellio. 



Fig. 43. Eight-celled stage of Armadillidium. 



Fig. 44. i6-celled stage of Porcellio. The lines joining the various cells in- 

 dicate their origin from the eight-celled stage. 



Fig. 45. i6-celled stage of Armadillidium, viewed from the posterior pole. 



Fig. 46. 32-celled stage of Armadillidium, viewed from the posterior pole. 



Fig. 47. Section through an ovum of Porcellio in the 32-celled stage. 



Fig. 48. Ovum of Porcellio in the 64-celled stage. 



Fig. 49. Ovum of Porcellio in the succeeding stage when the concentration 

 of the blastoderm around the mes-endoderm (nt-eii) is beginning. 



Fig. 50. Ovum oi Armadillidium in a stage slightly later than that of Fig. 49. 



Figs. 51 and 52. Still later stages of Armadillidium. 



Fig. 53. Blastoderm of Porcellio in situ. 



