PLATE X. 
Development of Smrcustipx (Lucifer). Figures from W. K. Brooks. 
Note. — The figures on this plate are copied from the original drawings. I am greatly indebted to Dr. Brooks for 
sending me his drawings and proof of the text of his memoir in advance of its appearance in the Philosophical Transactious 
of the Royal Society of London, 1882. The memoir is entitled “ Lucifer: a Study in Morphology.” 
a. Anus. n’. Supra-cesophageal nerve ganglion. 
al, First somite of abdomen. oc. Compound eye. 
at. Fourth somite of abdomen. ocl. Simple eye. 
ab. Abdomen. oes. Gsophagus. 
cp. Carapace. is Rostrum. 
ct. Embryonic cuticle. re. External branch of appendage. 
gm. Gastrula mouth. rt. Internal branch of appendage. 
h. Heart. st. Stomach. 
i. Intestine. a. Cells which form food-yolk, or possibly mesoblast. 
7b. Labrum. B. Auditory organ. 
1. Yolk-cells around stomach. Y- Antennal gland. 
mt. Metastoma. 3 Shell gland. 
nm.  Sub-cesophageal portion of nervous system. § Posterior extremity of abdomen or telson. 
The Roman numerals indicate the appendages of the body in their consecutive order; the Arabic numerals denote the 
somites. In Lucifer the thirteenth somite and its appendages (last thoracic) are not developed in any stage. 
1. Egg undergoing segmentation. There are eight segmentation spheres in the stage figured. The segmentation 
is regular and total, and a segmentation cavity is formed in the centre of the egg. 
2. Optical section of egg at later stage. One pole has become flattened, and the cell, a, which lies in the centre 
of the flattened area, has its broad end directed toward the segmentation cavity, while the other cells have 
their broad ends at the surface of the egg. Most of the food-yolk has disappeared from the other cells, 
which are now quite transparent, while the cell a contains as much food-yolk as ever. 
3. As the segmentation proceeds, the flattened area in fig. 2 becomes a deep pit, and a gastrula results as shown in 
fig. 3. The cell a divides in two and becomes pushed into the segmentation cavity. Whether the two 
cells a in fig. 3 represent the whole of the cell a in the preceding figure, or whether they are only the inner ends 
of the same, into which the deutoplasmic elements have withdrawn, and which have then become split off 
from the outer ends, was not determined. Their further history was not obtained. Brooks inclines to the 
belief that they represent the inner ends of the cell @ in fig. 2, and are not mesoblastic, but go to form a food- 
yolk like the inner ends of the yolk pyramids in centrolecithal eggs. 
4, Ventral view of embryo artificially removed from the egg thirty hours after oviposition. 76, labrum. © mt, 
metastoma. I, first antenna. II, second antenna. III, mandibles. IV, V, VI, buds representing the two 
pairs of maxille and the first pair of maxillipeds of the adult. When the embryo was set free, the body was 
enveloped in a delicate cuticle, which in the individual figured has been torn off from all the appendages 
except the first antenne. 
5. First free nauplius stage, about thirty-six hours after oviposition, lateral view. yoo in. long. The swim- 
ming appendages have become segmented, and the rudiment of the abdomen or telson () isapp:rent. The 
anus is yet absent. oc, ocellus. 
6. Second larval stage, or metanauplius, lateral view. yz 455 in. long. cp, carapace. oes, cesophagus. 7, intes- 
tine. 7, yolk-cells around the stomach (s/). 2, sub-cesophageal part of nervous cord. x’, supra-cesophageal 
nerve ganglion. The anus is now present on the ventral side of the terminal portion of the abdomen. 
7. Third larval stage, or first protozoéa stage, raised from the stage represented in fig. 6, dorsal view. 155 in. 
from tip of rostrum to base of spines on telson. The hind-body is now about as long as the carapace, 
and is divided into four somites and a long unsegmented portion (a6). The four somites (8-11) are those 
which subsequently bear the third pair of maxillipeds and the three following pairs of legs. A larva was taken 
from the sea agreeing with this one in size and every respect except that the free segments of the hind body 
were wanting. It is therefore probable that the larva figured is near the end of the first protozoéa stage. 
VII, second maxilliped. 7, rostrum. h, heart. The mandibles have become reduced to cutting blades in 
this stage. 
8. Fourth larval stage, or second protozoéa stage, raised from the preceding form, lateral view. x55y in. from 
tip of rostrum to fork of telson. oc, rudiment of compound eye. a, shell gland opening at the base of the 
first or second maxilla. 
