42 A. S. PACKARD, JR., ON THE ANATOMY 



Fio-. 3. A horizontal section through the emhiyo long before it hatches, before the body has become flat- 

 tened, before the heart and digestive canal have appeared, and soon after the embryo has reached the stage 

 represented by pbite 4, figs. 19, 19rt, of our first memoir. There are six cephalothoracic ganglia [I-VI] 

 besides the brain, and three abdominal ones [I-III] ; the first two abdominal ones corresponding to the 

 rudiments of the first and second abdominal appendages. 1-6, the six pairs of guathopods; I, II, the two 

 pairs of abdominal legs. 



Fig. 3(7. Enlarged view of the brain [?], the nerve cells [/<] forming the ganglion, which is enveloped by 

 connective tissue cells [c<]. (Is it these latter which are destined to form the nucleogenoiis bodies of the 

 adult brain ?) 



Fig. 4. Follicles at end of a semin.al tubule of testis of Limulus ; 4 a, epithelial cells of seminal tulmles, 

 nucleated and highly refractive; X Tolles' i objective C eye piece, magnified 72.5 diameters ; 46, amber- 

 colored pigment cells of testis ; 4c, similar but larger cells ; 4c?, spermatocysts of Limvdus ; 4e, cells associated 

 with the spermatocysts, with a large nucleus and a distinct nucleolus ; X Hartnack No. 9, B eyepiece. 



Fig. 5. Spermatocyst of a barnacle [Lepas], 5a, side view, and 5i, front view, of a spermatozoon of the 

 same; X -r^pB. 



Fig. 6. Spermatocysts of different shajies, a, b, c, c?, c (X ;^ B), and [_/"] tailless spermatozoon of Lihinia 

 canaliculata ; X Hartnack No. 9. 



Fig. 7. Su]>posed renal glands of Limulus; 5, one of the four lobes extending upwards from the main 

 stem [a] ; c, chitinous bases of the gnathopods. 7«, reddish ]iigmeut bodies coloring the cellular mass of the 

 gland, the cells being nucleated. Ih, Ic, two amber-colored yellow secreting cells scattered through the cel- 

 lular mass, composed of nucleated cells, as at 7a ; X Hartnack No. 9, B. 



Fig. 8. Tubules of liver of living Limulus; X 30 diameters ; 8r^, a parent cell of the smaller liver cells; 

 the shaded ones horn-colored, those unshaded clear ; 8i, free liver cell ; 8c, the same with jiale nuclei. 

 M, liver cells of Pano])oeus ; X J Tolles B. 



Fig. 9. Sections of liver tubes stained witli carmine ; X i A. 



Fig. 10. End of a liver tubule of Homarus umericanus; X i B. 



Fig. 11, 11«. Striated muscle near insertion of leg of Limulus; X ^ C (725 diameters). 



Fig. 12, 12a, l'2b. Sections through minute peri])heral arteries near the compound eye; X i A. 



Fig. 13. White fibrous cartilage of the supraneural cartilaginous plate; longitudinal section showing the 

 fibres on one edge and the nucleated cells in the dense structureless portion. 



Fig. 14. Portion of the blastoderm lying next to the chorion [cA] with yolk granules ; 14a, the same after 

 the outer layer [o] has begun to moult, the cells beginning to wrinkle on the edges, and being without the 

 protoplasmic granules [146] seen in the deeper layer of blastodermic cells ; 14c, vertical, and 14f/, profile view 

 of the same cells after moulting, the walls contracted and wrinkled, and with the nuclei jiartly absent or 

 absorbed ; X J A. 



Plate IV. 



Fig. 1. Section through the larva some time after hatching ; A<, heart ; inf, intestines; w,c, double nervous 

 cord; the muscular system well developed; aw, undeveloped adductor muscle. The parenchym of the 

 body consists of incijiient connective tissue and liver-cells. 



Fig. 2. Section through the cephalothorax of the same larva as represented at Fig. 1, the section passing 

 through the comiwund e^-e [cc], the heart [A<], proventrieulus [^w], and the double nervous cord; as yet 

 the neurilemma is unformeil, the nervous cord not being enveloped by it, this being represented by connec- 

 tive tissue [c<]. 



Fig. 3. Nerve cells of nervous cord of a freshly hatched larva, before the digestive tract and heart are 

 indicated ; 3a, connective tissue cells enveloping the nervous cord of 3 ; froui these cells the neurilemma is 

 probably formed. 



Fig. 4. An ocellus of a larval Limulus, showing the epithelial cells [p] and the dark pigment of the retina 

 M ) X J B. The ocelli are at this stage quite far apart. 



Fig. 5. Section of nervous cord [/;] embedded in connective tissue [c<], the section passing through the 

 body near the eyes of an advanced larva, in which the heart and digestive tract are developed. 



Fig. 6. Section through a ganglion [<7] of the same larva as represented in Fig. 5, the ganglion com- 

 pletely surrounded by the connective tissue [c<]. 



