168 SUMMARY OF CURRENT RESEARCHES RELATING TO 
thelium bears the functional secretory and small matrix cells, and there 
are also special accumulations of small cells forming “ gastric follicles.” 
Then follow a subepithelial connective layer, transverse muscles, more 
connective, longitudinal muscles, and ensheatliing connective. The 
changes in the secreting cells are discussed ; they conform with those 
described by Plateau, Frenzel, and others. The hind-gut varies not a 
little in different species ; a slender portion, a sac, and a rectum are 
present as in the larvse, and have similar functions. Indeed, the whole 
gut of the adult corresponds functionally and structurally with that of 
the larva. The gut of Anoxia and AnomaJa (and the Melolonthidaa 
generally) differs but slightly from that of Cetonia or Tropinota, but is 
more primitive than that of Oryctes or Phyllognatlius, facts which agree 
with the systematic relations of these genera. The surface or the length 
of the mid-gut increases as the nutritive value of the food diminishes. 
Mingazzini compares the salivary glands of Scardbseus with the salivary 
cells in Oryctes, Anoxia, &c., to show the gradual differentiation of these 
secretory structures. He is unable to find the fibrillar structure of the 
chitin described by Minot, nor does he believe in the existence of a 
chitinous stratum in the mid-gut, as maintained by Schneider. 
Coleopterous Larvae and their Relations to Adults.* — From the 
abstract of Mr. H. W. Conn’s paper we learn that he has arrived at 
certain conclusions ; they are based on the study of the larvae of beetles ; 
this group was selected as it shows the greatest amount of variation 
within a single order. A Campodeoid form was taken as the starting 
point, as it is the most widely distributed and has frequently been 
regarded as the closest living representative of the ancestral insect. 
AVith the exception of the Campodeoid type, which is found in a 
number of families, all beetle larvae have secondary modifications which 
have been introduced during the larval life of the beetles, and have 
never been represented by any adult features. Though they do not 
represent ancestral stages they may teach relationship, since the 
presence of a similar larva may indicate a recent common ancestor. 
Amid the immense variety of larvas four somewhat distinct types 
may be recognized ; there is the Campodeoid, a type slightly and 
variously modified from it, a Scarabid type, and a maggot-like type, like 
that of the weevils. In many cases it is possible to determine definitely 
the sort of conditions that have produced the present type. 
The division of larvae into types seems to have no relation to the 
classification of adult insects into suborders, but that of the families of 
larvae does run parallel to the classification of the families of adults. 
The many exceptions to this rule may, in part, be easily explained by 
differences in habit, and are most common in the degraded types of 
larv^. On the whole, the present larval types of beetles are about as 
old as the families, but not much older. If we adopt the present 
classification of adult beetles we must own that the amount of departure 
from the primitive larval type that any family of beetles present is no 
indication of the position in the scale of classification that the adults 
should occupy. It seems probable that the larva has been the first to 
modify its habits, and that the adult has subsequently acquired habits 
* Proc. Boston Soc. Nat. Hist., xxiv. (1889) pp. 42-5. 
