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



Fig. 3. A horizontal section through the embryo 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 plate 4, figs. 19, 19a, of our first memoir. There are six cephalothoracio 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 gnathopods; I, II, the two 

 pairs of abdominal legs. 



Fig. 3a. Enlarged view of the brain [?], the nerve cells [5] forming the ganglion, which is enveloped by 

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

 adult brain ?) 



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

 nucleated and highly refractive; X Tolles' J objective C eye jjiece, magnified 725 diameters ; 45, amber- 

 colored pigment cells of testis ; 4c, similar but larger cells ; id, sjsermatocysts of Limulus ; 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 56, front view, of a spermatozoon of the 

 same ; X t^^B. 



Fig. 6. Spermatocysts of different shapes, a, b, c, d, c (XJB), and [_/"] tailless spermatozoon of Iiibinia 

 canaliculata ; X Hartnack No. 9. 



Fig. 7. Supposed renal glands of Limulus ; 5, one of the four lobes extending upwards from the main 

 stem [a] ; c, ohitinous bases of the gnathopods. 7a, reddish pigment bodies coloring the cellular mass of the 

 gland, the cells being nucleated. 75, 7c, 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 ; 8a, a parent cell of the smaller liver cells ; 

 the shaded ones horn-colored, those unshaded clear; 85, free liver cell; 8c, the same'with pale nuclei. 

 8(?, Uver cells of Panopseus ; X \ ToUes B. 



Fig. 9. Sections of liver tubes stained with carmine ; X ^ A. 



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



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



Fig. 12, 12a, 125. Sections through minute joeripheral arteries near the compound eye; X |- 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 [145] seen in the deeper layer of blastodermic cells ; 14c, vertical, and lAd, profile view 

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

 absorbed ; X J A. 



Plate IV. 



Fig. 1. Section through the larva some time after hatching ; A<, heart; m«, intestines ; nc, double nervous 

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

 body consists of incipient 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 compound eye [cc], the heart \ht], proventriculus_[^r], and the double nervous cord ; as yet 

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

 tive tissue [ct]. 



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

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

 probably formed. 



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

 M j X ^ B. The ocelli are at this stage quite far apart. 



Fig. 5. Section of nervous cord [«.] embedded in connective tissue [ct], 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 [^] of the same larva as represented in Fig. 5, the ganglion com- 

 pletely surrounded by the connective tissue {ct\. 



