The concluding book from this trilogy is somewhat derivative, going beyond what is normal for pulp. In addition to the same problems as the previous book, this one takes highly questionable "evolution" to extremes - the female lead here was once an egg, then a tadpole, then aquatic lizard, ape, then human. Germans return in full villainy, but then this story was published in late 1918.

Taken as a whole, the series isn't bad - but isn't particularly good either. I would recommend reading just the first book, which comes to a fairly good conclusion with a few minor mysteries.