Packard.] 



60 [November 16, 



Dr. A. S. Packard, Jr., gave an account of the devel- 

 opment of Limulus Polyphemus, the Horse-Shoe crab. 



The eggs are laid near high tide mark, loose in the sand, late in 

 the spring and during June and July. The larva hatches in about 

 six weeks. Previous to hatching it bears a striking resemblance to 

 the Trilobites, and may also be compared with the fossil Carbonifer- 

 ous King Crab, Bellinurus. It passes through a very slight metamor- 

 phosis, consisting of the addition of three pairs of abdominal lamelli- 

 form feet, and is remarkably similar to the larval trilobite. For this 

 and other reasons he considered the Poeciloptera, or King Crabs and 

 their allies, the Eurypterus, Pterygotus, etc., to be a subdivision of 

 the Branchiopoda, which also includes the true Phyllopods and 

 Cladocera. 



He considered this order as having flourished most in Palssozoic 

 times, the living representatives being the remnants of an extensive 

 group, the missing links of which are to be sought among the Silu- 

 rian, Devonian, and Carboniferous strata. He regarded the known 

 forms as generalized types, which preceded in time and in process 

 of evolution the Decapod Crustacea. The Branchiopoda pass 

 through, either in the egg or in the larval state, a nauplius form; 

 and to such a form, probably living in the Laurentian seas, he would 

 trace the ancestry of the group, the order of descent being by per- 

 haps three or more parallel lines. Huxley has compared Pterygotus 

 t,o the zoea of a crab. The speaker extended this apt comparison to 

 the higher Branchiopoda, and the comparison does not apparently 

 fail when applied to Limulus, the larva of which is nearer a zoea than 

 a nauplius ; there being a pair of compound eyes, and a distinct 

 abdomen, bearing three pair of legs, while the cephalothoracic 

 appendages are comparable to the feet of the zoea of the Decapods, 

 which become by subsequent moults, mouth-organs, the true thoracic 

 feet being added at the first moult. He likened the Neuroptera and 

 Orthoptera, and, among Lepidoptera, the family Bombycidaj to the 

 Branchiopoda, the generic forms often widely differing among them- 

 selves, being in fact generalized types, the links connecting them 

 having probably perished in past geological periods. 



Dr. Packard also announced the recent discovery at Salem of a 

 new species of Pauropus, which he named Pauropus Lubbockii, in 

 honor of the discoverer of this most remarkable type of Myriapods, 

 which, as Lubbock has remarked, combines the characters of the 





