512 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



PLATE XXV. 



FIG. 1. Surface view of segment-in;: egg of Hippa hilptiidi-s. Thirty-two yolk pyramids present. 

 X3S. 



FIG-. 2. Embryo of Hippo tnlpt>i<li:t, .showing optic disks ami thoracic-abdominal plate. x38. 



FIG. 3. The central part of a transverse section of the ovary of tin- lolister, Homnrun americanus, 

 to show the progressive development of ova ; from the same series as that repre- 

 sented, with less enlargement, in Fig. (I. Ovary taken in January. x281. 



FIG. 4. Section of egg of Hippa h<lj><>i<l<'* in yolk segmentation. Sixty-four yolk pyramids pres- 

 enr. x70. 



FIG. 5. Part of segment in g egg ui Alpln'im minor, showing a single large nucleus and two smaller 

 nuclei. Compare with Fig. LiM. X-S1, 



FIG. 6. Central portion of transverse section of ovary of the lobster, corresponding nearly to that 

 shown in Fig. 3, showing the gerino-id'a! aieas and the irregularly radiating blood 

 sinuses. The diameter of the entire ovary is about twice that of the part represented. 

 The largest peripheral ova have an averaae diameter of about one thirty-third of an 

 inch, and their contents is only a bom. otiv-eighth that of the ripe egg. x TO. 



FIG. 7. Egg-nauplius embryo of 1-iip/xi Inlpoiilcx. Ajtpendages appear as simple buds. x3S. 



FIG. 8. Post-uauplins stage of Hippa. Abdomen bilobed at tip. ' Buds of ac least three pairs of 

 post-tnandibular appendages. Fi^s. 1, '_', 7, and 8 are made from pen-and-ink sketches, 

 and show only the general appearance of the embryo and its relation to the yolk. 



REFK RKN CK 1 . KTT EKS. 



.ll>. /'.. . linr.ii LC ;ilMloliilll:ll phlli-. 



II. '_'., lilc.oil cell. 



III. .S. , l>!(irnl Minus. 

 I'll., rhltiuulls i-iijiMhcll. 



I'll, jr., limiting membrane of blood Minns. 



<'l. N.. (ivai-ia.ii Hiroma. 



K. (., c'.nii i'nilirli-. 



F. (.'.. i-.jrg fdllirlc. 



Iri-r.. i;c'i iiiii-.'iial area. 



/. E.. nvariau stronia (undififerentiated). 



a. n 1 o~, nuclei of ovarian stroraa and developing e.ngs. 



<>. D., optic disk. 



II. L., optic lobe. 



r. P., yolk pyramid. 



T. S., yolk spherule. 



f'ac. , yolk vucuole. 



