1876.] Zoölogy. 689 
we are aware, are presented by the author, whose essay has, apparently, 
contrary to usage in German universities, been crowned not for the 
original work it contains but for the ideas suggested by the labors of pre- 
ceding authors. . 
In trying to reconstruct the form of the primitive insect, Mayer in- 
sists that it should be done from a study of the winged adult or imago, 
“since a priori we cannot know how far the form of the larva is original 
or secondary.” Other authors have with better reasons derived the an- 
cestral form from the larva. 
Mayer’s ancestral insect, then, which he calls Protentomon, had a body 
divided into a head, thorax, and abdomen, the latter consisting of 
eleven segments, while there were six thoracic feet with five-jointed tarsi, 
and two pairs of wings, nine (and perhaps eleven) pairs of stigmata, a pair 
of salivary glands, and four excretory organs or Malpighian vessels, be- 
sides a well-developed nervous system, heart, and an aaorta, as usual 
m existing insects. 
This hypothetical Protentomon is derived by Mayer from the worms,’ 
in opposition to the suggestions of Fritz Miiller and Brauer that the 
insects originated from the Crustacea. This worm (1), the parent of 
the half a million species of insects which have peopled the globe 
during the present and past ages, was “an unjointed worm, a common 
st.rting-point for the Tracheata and higher worms, and also a near 
relation of the ancestral form of the Crustacea.” This worm then (2) 
transformed into a higher organism, with eighteen joints to its body 
and at least fourteen pairs of segmental organs, with perhaps also a masti- 
catory apparatus in the form of jaws; and was perhaps nearly related to 
the existing Annelids. (3.) A third step towards the insects was a form 
similar to the second, but with ventral and perhaps also dorsal append- 
ages on all the segments ; it was still aquatic. It transformed (4) mio 
 Aworm with tracheæ and with dissimilar segments (the appendages ra 
_ Part beginning to disappear). It lived in fresh water. and is cal i 
our author Prototracheas. (5.) This Prototracheas became an Arc w 
tomon, still aquatic, with six feet, and clearly defined head, thorax, an 
‘ abdomen, Finally this fifth form acquired two pairs of wings, was terres- 
_ Malin its habits, and became (6) a Protentomon. f 
~ The author then discusses the ancestry of the different orders o 
iee It is noticeable that in treating of them he begins with the 
Hymenoptera and ends with the Neuroptera, following 1m fact, uncon- 
Slow y, the reviewer’s classification proposed in 1863. The aaa? 
: Neuroptera are, howev er, broken up into several orders, the aut or a 
_ ‘wing the usual German system; but Mayer is the first German a 4 
_ ™ far as we are aware, who places the Hymenoptera Mp: amaa 
hough Mayer does not mention it) in 
- ie Common Insects, chapter xiii., entitled Ancestry of Insects (1873). This 8 
: inexcusable since Dr. Mayer quotes from the essay. 
Yor. AiR 11. d 44 
a... 
his view was advocated by the writer (t 
