E. VON WILLEMOES-SUHM. 149 



describes it in the young Limulus which he figured in ' Cuvier's 

 Regne animal.' Only once I saw the edges ending in a rounded 

 point, a case which I think was due to a folding in of the skin, 

 and therefore could not be taken as evidence. In all the sub- 

 sequent free swimming stages the edges of the shield (the 

 diameter of which is 020 mm.) were round. The abdomen 

 shows its nine larval segments, and under the thin chitinous 

 covering you distinguish already clearly six newly formed seg- 

 ments, with lamellar appendages on all of them. The latter 

 can be best observed in a side view, when also the hairs or 

 their ends are already to be remarked. They consist of two 

 joints, the terminal being the shortest. 



The [region which simulated the] spine [of an adult Limu- 

 lus] being 0'056 mm. long [about one sixth of the whole length] 

 now shows eleven larval segments, with slightly serrated edges. 

 The terminal point has about the length of three of the pre- 

 ceding segments. 



The appendages are the same as in the former stages — the 

 three nauplial antennae. The eye also is still the simple Nau- 

 plius eye with a lens, but in one case we saw two lenses above 

 the black spot, perhaps the earliest trace of the later subdivi- 

 sion of the central eye into two. To the right and the left of 

 the eye there are still large globules of yolk, filling the cara- 

 pace. The organs of digestion show some changes, for the 

 upper part of the intestine is widened (the future muscular 

 stomach), and the position of the mouth, with which there is 

 as yet, however, no communication, is indicated by a chitinous 

 under lip. The anus is formed and communicates with the 

 intestine by a short rectum. It opens between two large 

 spines at the base of the last abdominal segment. Some yolk 

 globules are as yet left in the thorax, and some others are in- 

 cluded in the intestine. 



The fifth stage is signalised by the appearance of the two 

 large lateral eyes, which are situated a little below the base of 

 the first antennae. They consist of intensely black pigment, 

 and a circle round them indicates already the growing con- 

 nection between these large globular spots and the surface of 



