266 BULLETIN OF THE 
Edwards (No. 12, see p. 268) records a monstrosity affecting the eyo- 
stalk of Palinurus penicillatus ; and finally Packard (No. 17) has noticed 
a deformity of the caudal spine of Limulus Polyphemus. The last is 
probably not so rare as Packard supposes, as I have found two Specimens 
of Limulus with similarly deformed spines. There is also in the Museum 
of Comparative Zoology a small deformed specimen of Limulus Polyphe- 
mus, in which the left side of the gill-bearing segment of the body is 
marked by a deep concavity and absence of the lateral spines. Further, 
Figs. 2 and 8 on Plate TI. of this paper portray deformities of other parts 
than the great claws. Fig. 2 represents a monstrous condition of one of 
the small chelipeds of the lobster, and there is another specimen in the 
Museum in which the index or immovable finger of the chela of either 
the first or second pair of legs is double. Another lobster presents a. de- 
formity of one of the third pair of maxillipeds, the terminal segment 
being divided into three lobes. Plate II. fig. 8 represents a deformed 
lateral spine of the carapace of Callinectes hastatus. 
Reviewing all the deformities which have been described among Ar- 
thropods, I would divide them into five categories, as follows. 
Deformities : — a, of deficiency. 
b, of excess. 
c, of transformation. 
d, of arrested development. 
e, of hermaphroditism. 
a. In individuals affected with deformities of this class, certain parts 
normally present are wanting. Among Crustacea such cases are, as far 
as I am aware, never congenital, but result from accidental amputation 
of parts commonly restored by new growths, as before observed. 
b. Monstra per accessum. Under this head fall the majority of the 
monstrosities that have been described among Arthropods. Among 
insects the numerous cases recorded by Asmus,* Mocquerys,} various 
contributors to the Annales de la Société Entomologique de France, and 
lately by Jayne,f etc., etc., for the most part belong here. In these 
cases it is commonly the antenne and legs which are the seat of the 
monstrous developments, which usually take the form of a duplication, 
or even triplication, of the appendage. In most cases such double or 
triple appendages are single at the base, the duplication or triplication 
* Monstrositates Coleopterorum, 1835. 
T Recueil de Coléoptères anormaux, 1859. 
f Descriptions of some Monstrosities observed in North American Coleoptera, 
Trans. Amer, Ent. Soc, VIII. p. 155, 1880. 
